Iron-based sintered alloy having excellent machinability

ABSTRACT

This iron-based sintered alloy contains 0.05 to 3% by mass of calcium carbonate or 0.05 to 3% by mass of strontium carbonate. As a result, an iron-based sintered alloy having excellent machinability is obtained.

TECHNICAL FIELD

The present invention relates to an iron-based sintered alloy having excellent machinability which is used as materials for various machine components. This application claims priority from Japanese Patent Application No. 2003-62854 filed on Mar. 10, 2003, the disclosure of which is incorporated by reference herein.

BACKGROUND ART

With the progress of a sintering technique, various electric components such as yoke and rotor, and various machine components such as pistons for shock absorber, rod guides, bearing caps, valve plates for compressor, hubs, forkshifts, sprockets, toothed wheels, gears and synchronizer hubs have recently been produced using an iron-based sintered alloy obtained by sintering a raw powder mixture. For example, it is known that an iron-based sintered alloy having the composition consisting of pure iron and 0.1 to 1.5% by mass of P, the balance being Fe and inevitable impurities, is used to produce various electric components such as yokes and rotors. It is known that an iron-based sintered alloy having the composition consisting of 0.1 to 1.2% by mass of C, the balance being Fe and inevitable impurities, is used to produce pistons for shock absorber, and lot guides. It is known that an iron-based sintered alloy having the composition consisting of 0.1 to 1.2% by mass of C and 10 to 25% by mass of Cu, the balance being Fe and inevitable impurities, is used to produce bearing caps, and valve plates for compressor. It is known that an iron-based sintered alloy having the composition consisting of 0.1 to 1.2% by mass of C and 0.1 to 6% by mass of Cu, the balance being Fe and inevitable impurities, is used to produce forkshifts, sprockets, gears, toothed wheels, and pistons for shock absorber. It is known that an iron-based sintered alloy having the composition consisting of 0.1 to 1.2% by mass of C, 0.1 to 6% by mass of Cu, 0.1 to 10% by mass of Ni and 0.1 to 6% by mass of Mo, the balance being Fe and inevitable impurities, is used to produce CL cranks, sprockets, gears, and toothed wheels.

It is known that an iron-based sintered alloy having the composition consisting of 0.1 to 1.2% by mass of C and 0.1 to 6% by mass of Mo, the balance being Fe and inevitable impurities, an iron-based sintered alloy having the composition consisting of 0.1 to 1.2% by mass of C, 0.1 to 10% by mass of Cr and 0.1 to 6% by mass of Mo, the balance being Fe and inevitable impurities, an iron-based sintered alloy having the composition consisting of 0.1 to 1.2% by mass of C, 0.1 to 10% by mass of Ni, 0.1 to 10% by mass of Cr and 0.1 to 6% by mass of Mo, the balance being Fe and inevitable impurities, an iron-based sintered alloy having the composition consisting of 0.1 to 1.2% by mass of C, 0.1 to 6% by mass of Cu, 0.1 to 10% by mass of Ni, 0.1 to 10% by mass of Cr and 0.1 to 6% by mass of Mo, the balance being Fe and inevitable impurities, an iron-based sintered alloy having the composition consisting of 0.1 to 1.2% by mass of C and 0.1 to 10% by mass of Ni, the balance being Fe and inevitable impurities, an iron-based sintered alloy having the composition consisting of 0.1 to 1.2% by mass of C, 0.1 to 10% by mass of Ni and 0.1 to 6% by mass of Mo, the balance being Fe and inevitable impurities, and an iron-based sintered alloy having the composition consisting of 0.1 to 1.2% by mass of C, 0.1 to 6% by mass of Cu and 0.1 to 10% by mass of Ni, the balance being Fe and inevitable impurities, are used as materials of various machine components such as sprockets, gears and toothed wheels.

Also it is known that an iron-based sintered alloy having the composition consisting of 1.0 to 3.0% by mass of C, 0.5 to 8% by mass of Cu and 0.1 to 0.8% by mass of P, the balance being Fe and inevitable impurities, are used as materials of valve guides.

Also it is known that an iron-based sintered alloy having the composition consisting of 0.3 to 2.5% by mass of C, 0.5 to 12% by mass of Cr, 0.3 to 9% by mass of Mo, 3 to 14% by mass of W and 1 to 6% by mass of V, the balance being Fe and inevitable impurities, an iron-based sintered alloy having the composition consisting of 0.3 to 2.5% by mass of C, 0.5 to 12% by mass of Cr, 0.3 to 9% by mass of Mo, 3 to 14% by mass of W, 1 to 6% by mass of V and 5 to 14% by mass of Co, the balance being Fe and inevitable impurities, an iron-based sintered alloy having the composition consisting of 0.3 to 2% by mass of C, 0.5 to 10% by mass of Cr, 0.3 to 16% by mass of Mo and 0.1 to 5% by mass of Ni, and one or more kinds selected from among 1 to 5% by mass of W, 0.05 to 1% by mass of Si, 0.5 to 18% by mass of Co and 0.05 to 2% by mass of Nb, the balance being Fe and inevitable impurities, an iron-based sintered alloy having the composition consisting of 0.3 to 2% by mass of C, 0.5 to 10% by mass of Cr, 0.3 to 16% by mass of Mo and 0.1 to 5% by mass of Ni, one or more kinds selected from among 1 to 5% by mass of W, 0.05 to 1% by mass of Si, 0.5 to 18% by mass of Co and 0.05 to 2% by mass of Nb, and 10 to 20% by mass of Cu, the balance being Fe and inevitable impurities, and an iron-based sintered alloy having the composition consisting of 0.3 to 2% by mass of C, 0.1 to 3% by mass of Mo, 0.05 to 5% by mass of Ni and 0.1 to 2% by mass of Co, the balance being Fe and inevitable impurities, are used as materials of valve seats.

Also it is known that an iron-based sintered alloy having the composition consisting of 15 to 27% by mass of Cr and 3 to 29% by mass of Ni, the balance being Fe and inevitable impurities, an iron-based sintered alloy having the composition consisting of one or more kinds selected from among 15 to 27% by mass of Cr, 3 to 29% by mass of Ni, 0.5 to 7% by mass of Mo and 0.5 to 4% by mass of Cu, the balance being Fe and inevitable impurities, an iron-based sintered alloy having the composition consisting of 10 to 33% by mass of Cr, the balance being Fe and inevitable impurities, an iron-based sintered alloy having the composition consisting of 10 to 33% by mass of Cr and 0.5 to 3% by mass of Mo, the balance being Fe and inevitable impurities, an iron-based sintered alloy having the composition consisting of 10 to 33% by mass of Cr and 0.5 to 3% by mass of Mo, the balance being Fe and inevitable impurities, an iron-based sintered alloy having the composition consisting of 10 to 19% by mass of Cr and 0.05 to 1.3% by mass of C, the balance being Fe and inevitable impurities, an iron-based sintered alloy having the composition consisting of 14 to 19% by mass of Cr and 2 to 8% by mass of Ni, the balance being Fe and inevitable impurities, and an iron-based sintered alloy having the composition consisting of 14 to 19% by mass of Cr and 2 to 8% by mass of Ni, and one or more kinds selected from among 2 to 6% by mass of Cu, 0.1 to 0.5% by mass of Nb and 0.5 to 1.5% by mass of Al, the balance being Fe and inevitable impurities, are used as materials of corrosion-resistant machine components.

Various machine components made of these conventional iron-based sintered alloys are produced by blending predetermined raw powders, mixing the powders and compacting the powder mixture to obtain a green compact, and sintering the resulting green compact in a vacuum, dissociated ammonia gas, N₂+5% H₂ gas mixture, endothermic gas or exothermic gas atmosphere, and are finally shipped after piercing the required position using a drill and cutting or grinding the surface. Machining such as piercing, cutting or grinding is conducted by using various cutting tools. When machine components have a lot of positions to be cut, cutting tools are drastically worn out, resulting in high cost. Therefore, there has been made a trial of suppressing wear of the cutting tool by a method of adding about 1% of a MnS or MnO powder and sintering the resulting green compact thereby to improve machinability of the cutting tool (see Japanese Patent Application, First Publication No. Hei 3-267354) or a method of adding a CaO—MgO—SiO₂-based complex oxide, thereby to improve machinability (see Japanese Patent Application, First Publication No. Hei 8-260113) of the cutting tool, and thus reducing the cost.

DISCLOSURE OF THE INVENTION

An iron-based sintered alloy obtained by adding a conventional MnS powder, MnO powder or CaO—MgO—SiO₂-based complex oxide powder and sintering the resulting green compact has machinability, which is improved to some extent, but is not still satisfactory. Therefore, it is required to develop an iron-based sintered alloy having more excellent machinability.

From such a point of view, the present inventors have intensively studied so as to obtain an iron-based sintered alloy having more excellent machinability, which can be used as materials of various electric and machine components. As a result, they have found that an iron-based sintered alloy containing 0.05 to 3% by mass of a calcium carbonate powder or an iron-based sintered alloy containing 0.05 to 3% by mass of a strontium carbonate powder has more improved machinability.

The present invention has been made based on such a finding and is characterized by the followings:

-   (1) an iron-based sintered alloy having excellent machinability,     comprising 0.05 to 3% by mass of calcium carbonate, -   (2) an iron-based sintered alloy having excellent machinability with     the composition consisting of 0.05 to 3% by mass of calcium     carbonate, the balance being Fe and inevitable impurities, -   (3) an iron-based sintered alloy having excellent machinability with     the composition consisting of 0.05 to 3% by mass of calcium     carbonate and 0.1 to 1.5% by mass of P, the balance being Fe and     inevitable impurities, -   (4) an iron-based sintered alloy having excellent machinability with     the composition consisting of 0.05 to 3% by mass of calcium     carbonate and 0.1 to 1.2% by mass of C, the balance being Fe and     inevitable impurities, -   (5) an iron-based sintered alloy having excellent machinability with     the composition consisting of 0.05 to 3% by mass of calcium     carbonate, 0.1 to 1.2% by mass of C and 10 to 25% by mass of Cu, the     balance being Fe and inevitable impurities, -   (6) an iron-based sintered alloy having excellent machinability with     the composition consisting of 0.05 to 3% by mass of calcium     carbonate, 0.1 to 1.2% by mass of C and 0.1 to 6% by mass of Cu, the     balance being Fe and inevitable impurities, -   (7) an iron-based sintered alloy having excellent machinability with     the composition consisting of 0.05 to 3% by mass of calcium     carbonate, 0.1 to 1.2% by mass of C, 0.1 to 6% by mass of Cu, 0.1 to     10% by mass of Ni and 0.1 to 6% by mass of Mo, the balance being Fe     and inevitable impurities, -   (8) an iron-based sintered alloy having excellent machinability with     the composition consisting of 0.05 to 3% by mass of calcium     carbonate, 0.1 to 1.2% by mass of C and 0.1 to 6% by mass of Mo, the     balance being Fe and inevitable impurities, -   (9) an iron-based sintered alloy having excellent machinability with     the composition consisting of 0.05 to 3% by mass of calcium     carbonate, 0.1 to 1.2% by mass of C, 0.1 to 10% by mass of Cr and     0.1 to 6% by mass of Mo, the balance being Fe and inevitable     impurities, -   (10) an iron-based sintered alloy having excellent machinability     with the composition consisting of 0.05 to 3% by mass of calcium     carbonate, 0.1 to 1.2% by mass of C, 0.1 to 10% by mass of Ni, 0.1     to 10% by mass of Cr and 0.1 to 6% by mass of Mo, the balance being     Fe and inevitable impurities, -   (11) an iron-based sintered alloy having excellent machinability     with the composition consisting of 0.05 to 3% by mass of calcium     carbonate, 0.1 to 1.2% by mass of C, 0.1 to 6% by mass of Cu, 0.1 to     10% by mass of Ni, 0.1 to 10% by mass of Cr and 0.1 to 6% by mass of     Mo, the balance being Fe and inevitable impurities, -   (12) an iron-based sintered alloy having excellent machinability     with the composition consisting of 0.05 to 3% by mass of calcium     carbonate, 0.1 to 1.2% by mass of C and 0.1 to 10% by mass of Ni,     the balance being Fe and inevitable impurities, -   (13) an iron-based sintered alloy having excellent machinability     with the composition consisting of 0.05 to 3% by mass of calcium     carbonate, 0.1 to 1.2% by mass of C, 0.1 to 10% by mass of Ni and     0.1 to 6% by mass of Mo, the balance being Fe and inevitable     impurities, -   (14) an iron-based sintered alloy having excellent machinability     with the composition consisting of 0.05 to 3% by mass of calcium     carbonate, 0.1 to 1.2% by mass of C, 0.1 to 6% by mass of Cu and 0.1     to 10% by mass of Ni, the balance being Fe and inevitable     impurities, -   (15) an iron-based sintered alloy having excellent machinability     with the composition consisting of 0.05 to 3% by mass of calcium     carbonate, 1.0 to 3.0% by mass of C, 0.5 to 8% by mass of Cu and 0.1     to 0.8% by mass of P, the balance being Fe and inevitable     impurities, -   (16) an iron-based sintered alloy having excellent machinability     with the composition consisting of 0.05 to 3% by mass of calcium     carbonate, 0.3 to 2.5% by mass of C, 0.5 to 12% by mass of Cr, 0.3     to 9% by mass of Mo, 3 to 14% by mass of W and 1 to 6% by mass of V,     the balance being Fe and inevitable impurities, -   (17) an iron-based sintered alloy having excellent machinability     with the composition consisting of 0.05 to 3% by mass of calcium     carbonate, 0.3 to 2.5% by mass of C, 0.5 to 12% by mass of Cr, 0.3     to 9% by mass of Mo, 3 to 14% by mass of W, 1 to 6% by mass of V and     5 to 14% by mass of Co, the balance being Fe and inevitable     impurities, -   (18) an iron-based sintered alloy having excellent machinability     with the composition consisting of 0.05 to 3% by mass of calcium     carbonate, 0.3 to 2% by mass of C, 0.5 to 10% by mass of Cr, 0.3 to     16% by mass of Mo and 0.1 to 5% by mass of Ni, and one or more kinds     selected from among 1 to 5% by mass of W, 0.05 to 1% by mass of Si,     0.5 to 18% by mass of Co and 0.05 to 2% by mass of Nb, the balance     being Fe and inevitable impurities, -   (19) an iron-based sintered alloy having excellent machinability     with the composition consisting of 0.05 to 3% by mass of calcium     carbonate, 0.3 to 2% by mass of C, 0.5 to 10% by mass of Cr, 0.3 to     16% by mass of Mo and 0.1 to 5% by mass of Ni, one or more kinds     selected from among 1 to 5% by mass of W, 0.05 to 1% by mass of Si,     0.5 to 18% by mass of Co and 0.05 to 2% by mass of Nb, and 10 to 20%     by mass of Cu, the balance being Fe and inevitable impurities, -   (20) an iron-based sintered alloy having excellent machinability     with the composition consisting of 0.05 to 3% by mass of calcium     carbonate, 0.3 to 2% by mass of C, 0.1 to 3% by mass of Mo, 0.05 to     5% by mass of Ni and 0.1 to 2% by mass of Co, the balance being Fe     and inevitable impurities, -   (21) an iron-based sintered alloy having excellent machinability     with the composition consisting of 0.05 to 3% by mass of calcium     carbonate, 15 to 27% by mass of Cr and 3 to 29% by mass of Ni, the     balance being Fe and inevitable impurities, -   (22) an iron-based sintered alloy having excellent machinability     with the composition consisting of one or more kinds selected from     among 0.05 to 3% by mass of calcium carbonate, 15 to 27% by mass of     Cr, 3 to 29% by mass of Ni, 0.5 to 7% by mass of Mo and 0.5 to 4% by     mass of Cu, the balance being Fe and inevitable impurities, -   (23) an iron-based sintered alloy having excellent machinability     with the composition consisting of 0.05 to 3% by mass of calcium     carbonate and 10 to 33% by mass of Cr, the balance being Fe and     inevitable impurities, -   (24) an iron-based sintered alloy having excellent machinability     with the composition consisting of 0.05 to 3% by mass of calcium     carbonate, 10 to 33% by mass of Cr and 0.5 to 3% by mass of Mo, the     balance being Fe and inevitable impurities, -   (25) an iron-based sintered alloy having excellent machinability     with the composition consisting of 0.05 to 3% by mass of calcium     carbonate, 10 to 19% by mass of Cr and 0.05 to 1.3% by mass of C,     the balance being Fe and inevitable impurities, -   (26) an iron-based sintered alloy having excellent machinability     with the composition consisting of 0.05 to 3% by mass of calcium     carbonate, 14 to 19% by mass of Cr and 2 to 8% by mass of Ni, the     balance being Fe and inevitable impurities, -   (27) an iron-based sintered alloy having excellent machinability     with the composition consisting of 0.05 to 3% by mass of calcium     carbonate, 14 to 19% by mass of Cr and 2 to 8% by mass of Ni, and     one or more kinds selected from among 2 to 6% by mass of Cu, 0.1 to     0.5% by mass of Nb and 0.5 to 1.5% by mass of Al, the balance being     Fe and inevitable impurities, -   (28) an iron-based sintered alloy having excellent machinability,     comprising 0.05 to 3% by mass of strontium carbonate, -   (29) an iron-based sintered alloy having excellent machinability     with the composition consisting of 0.05 to 3% by mass of strontium     carbonate, the balance being Fe and inevitable impurities, -   (30) an iron-based sintered alloy having excellent machinability     with the composition consisting of 0.05 to 3% by mass of strontium     carbonate and 0.1 to 1.5% by mass of P, the balance being Fe and     inevitable impurities, -   (31) an iron-based sintered alloy having excellent machinability     with the composition consisting of 0.05 to 3% by mass of strontium     carbonate and 0.1 to 1.2% by mass of C, the balance being Fe and     inevitable impurities, -   (32) an iron-based sintered alloy having excellent machinability     with the composition consisting of 0.05 to 3% by mass of strontium     carbonate, 0.1 to 1.2% by mass of C and 10 to 25% by mass of Cu, the     balance being Fe and inevitable impurities, -   (33) an iron-based sintered alloy having excellent machinability     with the composition consisting of 0.05 to 3% by mass of strontium     carbonate, 0.1 to 1.2% by mass of C and 0.1 to 6% by mass of Cu, the     balance being Fe and inevitable impurities, -   (34) an iron-based sintered alloy having excellent machinability     with the composition consisting of 0.05 to 3% by mass of strontium     carbonate, 0.1 to 1.2% by mass of C, 0.1 to 6% by mass of Cu, 0.1 to     10% by mass of Ni and 0.1 to 6% by mass of Mo, the balance being Fe     and inevitable impurities, -   (35) an iron-based sintered alloy having excellent machinability     with the composition consisting of 0.05 to 3% by mass of strontium     carbonate, 0.1 to 1.2% by mass of C and 0.1 to 6% by mass of Mo, the     balance being Fe and inevitable impurities, -   (36) an iron-based sintered alloy having excellent machinability     with the composition consisting of 0.05 to 3% by mass of strontium     carbonate, 0.1 to 1.2% by mass of C, 0.1 to 10% by mass of Cr and     0.1 to 6% by mass of Mo, the balance being Fe and inevitable     impurities, -   (37) an iron-based sintered alloy having excellent machinability     with the composition consisting of 0.05 to 3% by mass of strontium     carbonate, 0.1 to 1.2% by mass of C, 0.1 to 10% by mass of Ni, 0.1     to 10% by mass of Cr and 0.1 to 6% by mass of Mo, the balance being     Fe and inevitable impurities, -   (38) an iron-based sintered alloy having excellent machinability     with the composition consisting of 0.05 to 3% by mass of strontium     carbonate, 0.1 to 1.2% by mass of C, 0.1 to 6% by mass of Cu, 0.1 to     10% by mass of Ni, 0.1 to 10% by mass of Cr and 0.1 to 6% by mass of     Mo, the balance being Fe and inevitable impurities, -   (39) an iron-based sintered alloy having excellent machinability     with the composition consisting of 0.05 to 3% by mass of strontium     carbonate, 0.1 to 1.2% by mass of C and 0.1 to 10% by mass of Ni,     the balance being Fe and inevitable impurities, -   (40) an iron-based sintered alloy having excellent machinability     with the composition consisting of 0.05 to 3% by mass of strontium     carbonate, 0.1 to 1.2% by mass of C, 0.1 to 10% by mass of Ni and     0.1 to 6% by mass of Mo, the balance being Fe and inevitable     impurities, -   (41) an iron-based sintered alloy having excellent machinability     with the composition consisting of 0.05 to 3% by mass of strontium     carbonate, 0.1 to 1.2% by mass of C, 0.1 to 6% by mass of Cu and 0.1     to 10% by mass of Ni, the balance being Fe and inevitable     impurities, -   (42) an iron-based sintered alloy having excellent machinability     with the composition consisting of 0.05 to 3% by mass of strontium     carbonate, 1.0 to 3.0% by mass of C, 0.5 to 8% by mass of Cu and 0.1     to 0.8% by mass of P, the balance being Fe and inevitable     impurities, -   (43) an iron-based sintered alloy having excellent machinability     with the composition consisting of 0.05 to 3% by mass of strontium     carbonate, 0.3 to 2.5% by mass of C, 0.5 to 12% by mass of Cr, 0.3     to 9% by mass of Mo, 3 to 14% by mass of W and 1 to 6% by mass of V,     the balance being Fe and inevitable impurities, -   (44) an iron-based sintered alloy having excellent machinability     with the composition consisting of 0.05 to 3% by mass of strontium     carbonate, 0.3 to 2.5% by mass of C, 0.5 to 12% by mass of Cr, 0.3     to 9% by mass of Mo, 3 to 14% by mass of W, 1 to 6% by mass of V and     5 to 14% by mass of Co, the balance being Fe and inevitable     impurities, -   (45) an iron-based sintered alloy having excellent machinability     with the composition consisting of 0.05 to 3% by mass of strontium     carbonate, 0.3 to 2% by mass of C, 0.5 to 10% by mass of Cr, 0.3 to     16% by mass of Mo and 0.1 to 5% by mass of Ni, and one or more kinds     selected from among 1 to 5% by mass of W, 0.05 to 1% by mass of Si,     0.5 to 18% by mass of Co and 0.05 to 2% by mass of Nb, the balance     being Fe and inevitable impurities, -   (46) an iron-based sintered alloy having excellent machinability     with the composition consisting of 0.05 to 3% by mass of strontium     carbonate, 0.3 to 2% by mass of C, 0.5 to 10% by mass of Cr, 0.3 to     16% by mass of Mo and 0.1 to 5% by mass of Ni, one or more kinds     selected from among 1 to 5% by mass of W, 0.05 to 1% by mass of Si,     0.5 to 18% by mass of Co and 0.05 to 2% by mass of Nb, and 10 to 20%     by mass of Cu, the balance being Fe and inevitable impurities, -   (47) an iron-based sintered alloy having excellent machinability     with the composition consisting of 0.05 to 3% by mass of strontium     carbonate, 0.3 to 2% by mass of C, 0.1 to 3% by mass of Mo, 0.05 to     5% by mass of Ni and 0.1 to 2% by mass of Co, the balance being Fe     and inevitable impurities, -   (48) an iron-based sintered alloy having excellent machinability     with the composition consisting of 0.05 to 3% by mass of strontium     carbonate, 15 to 27% by mass of Cr and 3 to 29% by mass of Ni, the     balance being Fe and inevitable impurities, -   (49) an iron-based sintered alloy having excellent machinability     with the composition consisting of one or more kinds selected from     among 0.05 to 3% by mass of strontium carbonate, 15 to 27% by mass     of Cr, 3 to 29% by mass of Ni, 0.5 to 7% by mass of Mo and 0.5 to 4%     by mass of Cu, the balance being Fe and inevitable impurities, -   (50) an iron-based sintered alloy having excellent machinability     with the composition consisting of 0.05 to 3% by mass of strontium     carbonate and 10 to 33% by mass of Cr, the balance being Fe and     inevitable impurities, -   (51) an iron-based sintered alloy having excellent machinability     with the composition consisting of 0.05 to 3% by mass of strontium     carbonate, 10 to 33% by mass of Cr and 0.5 to 3% by mass of Mo, the     balance being Fe and inevitable impurities, -   (52) an iron-based sintered alloy having excellent machinability     with the composition consisting of 0.05 to 3% by mass of strontium     carbonate, 10 to 19% by mass of Cr and 0.05 to 1.3% by mass of C,     the balance being Fe and inevitable impurities, -   (53) an iron-based sintered alloy having excellent machinability     with the composition consisting of 0.05 to 3% by mass of strontium     carbonate, 14 to 19% by mass of Cr and 2 to 8% by mass of Ni, the     balance being Fe and inevitable impurities, and -   (54) an iron-based sintered alloy having excellent machinability     with the composition consisting of 0.05 to 3% by mass of strontium     carbonate, 14 to 19% by mass of Cr and 2 to 8% by mass of Ni, and     one or more kinds selected from among 2 to 6% by mass of Cu, 0.1 to     0.5% by mass of Nb and 0.5 to 1.5% by mass of Al, the balance being     Fe and inevitable impurities.

The iron-based sintered alloys having excellent machinability, which contain 0.05 to 3% by mass of calcium carbonate, according to (1) to (27) of the present invention are produced by blending a calcium carbonate powder having an average particle size of 0.1 to 30 μm with raw powders, mixing these powders and compacting the powder mixture to obtain a green compact, and sintering the resulting green compact in an atmosphere of a nonoxidizing gas such as vacuum, dissociated ammonia gas, N₂+5% H₂ gas mixture, endothermic gas or exothermic gas. The green compact is particularly preferably sintered in an atmosphere of the nonoxidizing gas such as endothermic gas or exothermic gas. The iron-based sintered alloy thus obtained has a structure in which CaCO₃ is dispersed at grain boundary in a basis material of the iron-based sintered alloy. The presence of CaCO₃ in the sintered compact obtained by sintering the green compact can be confirmed by X-ray diffraction.

The iron-based sintered alloys having excellent machinability, which contain 0.05 to 3% by mass of strontium carbonate, according to (28) to (54) of the present invention are produced by blending a strontium carbonate powder having an average particle size of 0.1 to 30 μm with raw powders, mixing these powders and compacting the powder mixture to obtain a green compact, and sintering the resulting green compact in an atmosphere of a nonoxidizing gas such as vacuum, dissociated ammonia gas, N₂+5% H₂ gas mixture, endothermic gas or exothermic gas. The green compact is particularly preferably sintered in an atmosphere of the nonoxidizing gas such as endothermic gas or exothermic gas. The iron-based sintered alloy thus obtained has a structure in which SrCO₃ is dispersed at grain boundary in a basis material of the iron-based sintered alloy. The presence of SrCO₃ in the sintered compact obtained by sintering the green compact can be confirmed by X-ray diffraction.

Therefore, the present invention is characterized by the followings: (55) a method for preparing the iron-based sintered alloy having excellent machinability according to any one of (1) to (27), which comprises compacting a raw powder mixture containing 0.05 to 3% by mass of a calcium carbonate powder having an average particle size of 0.1 to 30 μm as a raw powder to obtain a green compact and sintering the resulting green compact in a nonoxidizing gas atmosphere, and (56) a method for preparing the iron-based sintered alloy having excellent machinability according to any one of (28) to (54), which comprises compacting a raw powder mixture containing 0.05 to 3% by mass of a strontium carbonate powder having an average particle size of 0.1 to 30 μm as a raw powder to obtain a green compact and sintering the resulting green compact in a nonoxidizing gas atmosphere.

The average particle size of the calcium carbonate powder as the raw powder was defined within a range from 0.1 to 30 μm by the following reason. That is, when the average particle size of the calcium carbonate powder exceeds 30 μm, a contact area between the calcium carbonate powder and the basis material decreases and sufficient machinability improving effect is not exerted. On the other hand, when the average particle size of the calcium carbonate powder is less than 0.1 μm, a force of agglomeration increases, and thus the calcium carbonate powder is not uniformly dispersed in the basis material and further machinability improving effect is not exerted, and it is not preferred.

The average particle size of the strontium carbonate powder as the raw powder was defined within a range from 0.1 to 30 μm by the following reason. That is, when the average particle size of the strontium carbonate powder exceeds 30 μm, a contact area between the strontium carbonate powder and the basis material decreases and sufficient machinability improving effect is not exerted. On the other hand, when the average particle size of the strontium carbonate powder is less than 0.1 μm, a force of agglomeration increases, and thus the strontium carbonate powder is not uniformly dispersed in the basis material and further machinability improving effect is not exerted, and it is not preferred.

The endothermic gas is a gas containing, as a main component, hydrogen, carbon monoxide and nitrogen, which is obtained by mixing a natural gas, propane, butane or coke oven gas with an air to obtain a gas mixture, and decomposing and converting the gas mixture while passing through a heated catalyst composed mainly of nickel. In this case, since this reaction is an endothermic reaction, a catalyst layer must be heated. The exothermic gas is a gas containing nitrogen as a main component, hydrogen and carbon monoxide, which is obtained by semicombusting a natural gas, propane, butane or coke oven gas with air, and decomposing and converting the combustion gas while passing through a nickel catalyst layer or charcoal layer. In this case, since the temperature of the catalyst increases due to combustion heat of the raw gas, it is not necessary to externally heat the catalyst layer.

The sintering temperature, at which the iron-based sintered alloy having excellent machinability is sintered, is preferably from 1100 to 1300° C. (more preferably from 1110 to 1250° C.) and this sintering temperature is the temperature which is generally known as a temperature at which the iron-based sintered alloy is sintered.

The reason why the composition of the CaCO₃ component and the composition of the SrCO₃ component in the iron-based sintered alloy having excellent machinability of the present invention were as limited as described above will now be described.

CaCO₃ has such an effect that it exists at grain boundary and is uniformly dispersed in a basis material, thereby to improve machinability. When the content is less than 0.05% by mass, sufficient machinability improving effect is not exerted. On the other hand, even when the content exceeds 3.0% by mass, further machinability improving effect is not exerted and the strength of the iron-based sintered alloy rather decreases, and therefore it is not preferred. Therefore, the content of CaCO₃ in the iron-based sintered alloy of the present invention was defined within a range from 0.05 to 3.0% by mass. The content of CaCO₃ is more preferably within a range from 0.1 to 2% by mass.

SrCO₃ has such an effect that it exists at grain boundary and is uniformly dispersed in a basis material, thereby to improve machinability. When the content is less than 0.05% by mass, sufficient machinability improving effect is not exerted. On the other hand, even when the content exceeds 3.0% by mass, further machinability improving effect is not exerted and the strength of the iron-based sintered alloy rather decreases, and therefore it is not preferred. Therefore, the content of SrCO₃ in the iron-based sintered alloy of the present invention was defined within a range from 0.05 to 3.0% by mass. The content of SrCO₃ is more preferably within a range from 0.1 to 2% by mass.

BEST MODE FOR CARRYING OUT THE INVENTION

Preferred examples of the present invention will now be described with reference to the accompanying drawings. The present invention is not limited to the following examples and, for example, constituent features of these examples may be appropriately combined with each other.

EXAMPLE 1

As raw powders, a CaCO₃ powder having an average particle size shown in Table 1, a CaMgSiO₄ powder having an average particle size of 10 μm, a MnS powder having an average particle size of 20 μm, a CaF₂ powder having an average particle size of 36 μm and a pure Fe powder having an average particle size of 80 μm were prepared. These raw powders were blended according to the formulation shown in Table 1, mixed in a double corn mixer and compacted to obtain a green compact, and then the resulting green compact was sintered in an endothermic gas (ratio of components=H₂: 40.5%, CO: 19.8%, CO₂: 0.1%, CH: 0.5%, and N₂: 39.1%) atmosphere under the conditions of a temperature of 1120° C. and a retention time of 20 minutes to obtain iron-based sintered alloys 1 to 10 of the present invention, comparative sintered alloys 1 to 2, and conventional sintered alloys 1 to 3.

Cylindrical sintered alloy blocks for piercing test each having a diameter of 30 mm and a height of 10 mm, made of the sintered alloys 1 to 10 of the present invention, the comparative sintered alloys 1 to 2, and the conventional sintered alloys 1 to 3 were produced and these cylindrical sintered alloy blocks for piercing test were repeatedly pierced until the drill is damaged, using a high-speed steel drill having a diameter of 1.2 mm, under the following conditions:

-   Rotating speed: 10000 rpm -   Feed speed: 0.030 mm/rev. -   Cutting oil: none (dry).

The number of piercing (maximum number of piercing, lifetime) of one new drill was measured. The results are shown in Table 1. Machinability was evaluated by the results. TABLE 1 Component ratio of Component ratio of raw powder iron-based (mass %) sintered alloy (mass %) CaCO₃ powder Fe Average particle and Number of Iron-based sintered size is described inevitable piercing alloy in parenthesis. Fe powder CaCO₃ impurities (times) Remarks Products of the 1  0.05 (0.1 μm) balance 0.03 balance 59 — present invention 2  0.2 (0.1 μm) balance 0.18 balance 137 — 3  0.5 (0.6 μm) balance 0.48 balance 155 — 4  1.0 (2 μm) balance 0.95 balance 203 — 5  1.3 (0.6 μm) balance 1.26 balance 196 — 6  1.5 (2 μm) balance 1.48 balance 236 — 7  1.8 (18 μm) balance 1.76 balance 213 — 8  2.1 (2 μm) balance 1.99 balance 176 — 9  2.5 (18 μm) balance 2.43 balance 222 — 10   3.0 (30 μm) balance 2.97 balance 310 — Comparative 1 0.02* (40 μm*) balance 0.01 balance 23 — products 2  3.5* (0.01 μm*) balance  3.45* balance 114 decrease in strength Conventional 1 CaMgSi₄:1 balance CaMgSi₄:1 balance 38 — products 2 MnS:1 balance MnS:0.97 balance 27 — 3 CaF₂:1 balance CaF₂:1 balance 25 — The symbol * means the value which is not within the scope of the present invention.

As is apparent from the results shown in Table 1, the number of piercing of the cylindrical sintered alloy blocks for piercing test made of the sintered alloys 1 to 10 of the present invention is larger than that of the cylindrical sintered alloy blocks for piercing test made of the conventional sintered alloys 1 to 3 and therefore the sintered alloys of the present invention are excellent in machinability. However, the comparative sintered alloy 1 containing CaCO₃ in the content of less than the range defined in the present invention is inferior in machinability because of small number of piercing, while the comparative sintered alloy 2 containing CaCO₃ in the content of more than the range defined in the present invention is excellent in machinability because of large number of piercing, but shows drastically decreased deflection strength, and therefore it is not preferred.

EXAMPLE 2

As raw powders, a CaCO₃ powder having an average particle size shown in Table 2, a CaMgSiO₄ powder having an average particle size of 10 μm, a MnS powder having an average particle size of 20 μm, a CaF₂ powder having an average particle size of 36 μm and a Fe-0.6 mass % P powder having an average particle size of 80 μm were prepared. These raw powders were blended according to the formulation shown in Table 2, mixed in a double corn mixer and compacted to obtain a green compact, and then the resulting green compact was sintered in an endothermic gas (ratio of components=H₂: 40.5%, CO: 19.8%, CO₂: 0.1%, CH: 0.5%, and N₂: 39.1%) atmosphere under the conditions of a temperature of 1120° C. and a retention time of 20 minutes to obtain iron-based sintered alloys 11 to 20 of the present invention, comparative sintered alloys 3 to 4, and conventional sintered alloys 4 to 6.

Cylindrical sintered alloy blocks for piercing test each having a diameter of 30 mm and a height of 10 mm, made of the sintered alloys 11 to 20 of the present invention, the comparative sintered alloys 3 to 4, and the conventional sintered alloys 4 to 6 were produced and these cylindrical sintered alloy blocks for piercing test were repeatedly pierced until the drill is damaged, using a high-speed steel drill having a diameter of 1.2 mm, under the following conditions:

-   Rotating speed: 10000 rpm -   Feed speed: 0.030 mm/rev. -   Cutting oil: none (dry).

The number of piercing (maximum number of piercing, lifetime) of one new drill was measured. The results are shown in Table 2. Machinability was evaluated by the results. TABLE 2 Component ratio of Component ratio of raw powder iron-based sintered alloy (mass %) (mass %) CaCO₃ powder Fe Average particle Fe-based and Number of Iron-based sintered size is described alloy inevitable piercing alloy in parenthesis. powder# CaCO₃ P impurities (times) Remarks Products of the 11  0.05 (0.1 μm) balance 0.03 0.55 balance 51 — present invention 12  0.2 (0.1 μm) balance 0.18 0.58 balance 119 — 13  0.5 (0.6 μm) balance 0.48 0.53 balance 158 — 14  1.0 (2 μm) balance 0.95 0.53 balance 176 — 15  1.3 (0.6 μm) balance 1.28 0.57 balance 140 — 16  1.5 (2 μm) balance 1.48 0.57 balance 131 — 17  1.8 (18 μm) balance 1.76 0.54 balance 167 — 18  2.1 (2 μm) balance 1.99 0.53 balance 121 — 19  2.5 (18 μm) balance 2.42 0.55 balance 137 — 20  3.0 (30 μm) balance 2.97 0.55 balance 186 — Comparative 3 0.02* (40 μm*) balance  0.01* 0.56 balance 27 — products 4  3.5* (0.01 μm*) balance  3.42* 0.54 balance 125 decrease in strength Conventional 4 CaMgSi₄:1 balance CaMgSi₄:1 0.55 balance 33 — products 5 MnS:1 balance MnS:0.97 0.55 balance 35 — 6 CaF₂:1 balance CaF₂:1 0.55 balance 22 — The symbol * means the value which is not within the scope of the present invention. #Fe-based alloy powder with the composition of Fe—0.6 mass % P

As is apparent from the results shown in Table 2, the number of piercing of the cylindrical sintered alloy blocks for piercing test made of the sintered alloys 11 to 20 of the present invention is larger than that of the cylindrical sintered alloy blocks for piercing test made of the conventional sintered alloys 4 to 6 and therefore the sintered alloys of the present invention are excellent in machinability. However, the comparative sintered alloy 3 containing CaCO₃ in the content of less than the range defined in the present invention is inferior in machinability because of small number of piercing, while the comparative sintered alloy 4 containing CaCO₃ in the content of more than the range defined in the present invention is excellent in machinability because of large number of piercing, but shows drastically decreased deflection strength, and therefore it is not preferred.

EXAMPLE 3

As raw powders, a CaCO₃ powder having an average particle size shown in Table 3, a CaMgSiO₄ powder having an average particle size of 10 μm, a MnS powder having an average particle size of 20 μm, a CaF₂ powder having an average particle size of 36 μm, a Fe powder having an average particle size of 80 μm and a C powder having an average particle size of 18 μm were prepared. These raw powders were blended according to the formulation shown in Table 3, mixed in a double corn mixer and compacted to obtain a green compact, and then the resulting green compact was sintered in an endothermic gas (ratio of components=H₂: 40.5%, CO: 19.8%, CO₂: 0.1%, CH: 0.5%, and N₂: 39.1%) atmosphere under the conditions of a temperature of 1120° C. and a retention time of 20 minutes to obtain iron-based sintered alloys 21 to 30 of the present invention, comparative sintered alloys 5 to 6, and conventional sintered alloys 7 to 9.

Cylindrical sintered alloy blocks for piercing test each having a diameter of 30 mm and a height of 10 mm, made of the sintered alloys 21 to 30 of the present invention, the comparative sintered alloys 5 to 6, and the conventional sintered alloys 7 to 9 were produced and these cylindrical sintered alloy blocks for piercing test were repeatedly pierced until the drill is damaged, using a high-speed steel drill having a diameter of 1.2 mm, under the following conditions:

-   Rotating speed: 10000 rpm -   Feed speed: 0.018 mm/rev. -   Cutting oil: none (dry).

The number of piercing (maximum number of piercing, lifetime) of one new drill was measured. The results are shown in Table 3. Machinability was evaluated by the results. TABLE 3 Component ratio of Component ratio of iron-based raw powder (mass %) sintered alloy (mass %) CaCO₃ powder Fe Average particle and Number of Iron-based sintered size is described C Fe inevitable piercing alloy in parenthesis. powder powder CaCO₃ C impurities (times) Remarks Products of the 21 0.05 (0.1μm) 0.13 balance 0.03 0.11 balance 80 — present invention 22 0.2 (0.1 μm) 0.3 balance 0.17 0.24 balance 102 — 23 0.5 (0.6 μm) 0.6 balance 0.47 0.54 balance 95 — 24 1.0 (2 μm) 0.8 balance 0.94 0.55 balance 135 — 25 1.3 (0.6 μm) 1.1 balance 1.22 1.02 balance 197 — 26 1.5 (2 μm) 1.1 balance 1.43 0.99 balance 208 — 27 1.8 (18 μm) 1.1 balance 1.69 1.05 balance 191 — 28 2.1 (2 μm) 1.1 balance 2.09 1.03 balance 220 — 29 2.5 (18 μm) 1.1 balance 2.3  1.03 balance 174 — 30 3.0 (30 μm) 1.2 balance 2.91 1.15 balance 180 — Comparative 5 0.02* (40 μm*) 1.1 balance  0.01* 1.04 balance 22 — products 6 3.5* (0.01 μm*) 1.1 balance  3.38* 1.01 balance 126 decrease in strength Conventional 7 CaMgSi₄:1 (10 μm) 1.1 balance CaMgSi₄:1 1.04 balance 37 — products 8 MnS:1 (20 μm) 1.1 balance MnS:0.97 1.04 balance 45 — 9 CaF₂:1 (36 μm) 1.1 balance CaF₂:1 1.04 balance 29 — The symbol * means the value which is not within the scope of the present invention.

As is apparent from the results shown in Table 3, the number of piercing of the cylindrical sintered alloy blocks for piercing test made of the sintered alloys 21 to 30 of the present invention is larger than that of the cylindrical sintered alloy blocks for piercing test made of the conventional sintered alloys 7 to 9 and therefore the sintered alloys of the present invention are excellent in machinability. However, the comparative sintered alloy 5 containing CaCO₃ in the content of less than the range defined in the present invention is inferior in machinability because of small number of piercing, while the comparative sintered alloy 6 containing CaCO₃ in the content of more than the range defined in the present invention is excellent in machinability because of large number of piercing, but shows drastically decreased deflection strength, and therefore it is not preferred.

EXAMPLE 4

As raw powders, a CaCO₃ powder having an average particle size shown in Table 4, a CaMgSiO₄ powder having an average particle size of 10 μm, a MnS powder having an average particle size of 20 μm, a CaF₂ powder having an average particle size of 36 μm, a Fe powder having an average particle size of 80 μm and a C powder having an average particle size of 18 μm were prepared. These raw powders were blended according to the formulation shown in Table 4, mixed in a double corn mixer and compacted to obtain a green compact, and then the resulting green compact was sintered in an endothermic gas (ratio of components=H₂: 40.5%, CO: 19.8%, CO₂: 0.1%, CH: 0.5%, and N₂: 39.1%) atmosphere under the conditions of a temperature of 1120° C. and a retention time of 20 minutes and subjected to 20% Cu infiltration to obtain iron-based sintered alloys 31 to 40 of the present invention, comparative sintered alloys 7 to 8, and conventional sintered alloys 10 to 12.

Cylindrical sintered alloy blocks for piercing test each having a diameter of 30 mm and a height of 10 mm, made of the sintered alloys 31 to 40 of the present invention, the comparative sintered alloys 7 to 8, and the conventional sintered alloys 10 to 12 were produced and these cylindrical sintered alloy blocks for piercing test were repeatedly pierced until the drill is damaged, using a high-speed steel drill having a diameter of 1.2 mm, under the following conditions:

-   Rotating speed: 10000 rpm -   Feed speed: 0.018 mm/rev. -   Cutting oil: none (dry).

The number of piercing (maximum number of piercing, lifetime) of one new drill was measured. The results are shown in Table 4. Machinability was evaluated by the results. TABLE 4 Component ratio Component ratio of iron-based sintered of raw powder (mass %) alloy (mass %) CaCO₃ powder Fe Number Average particle and of Iron-based sintered size is described Infiltration inevitable piercing alloy in parenthesis. C powder Fe powder Cu CaCO₃ C Cu impurities (times) Remarks Products of the 31 0.05 (0.1 μm) 0.13 balance 20 0.05 0.12 19.5 balance 78 — present 32 0.2 (0.5 μm) 0.3 balance 20 0.20 0.24 20.2 balance 126 — invention 33 0.5 (1 μm) 0.6 balance 20 0.49 0.54 20.1 balance 186 — 34 1.0 (2 μm) 0.8 balance 20 0.97 0.75 19.6 balance 201 — 35 1.3 (0.5 μm) 1.1 balance 20 1.28 1.05 19.9 balance 210 — 36 1.5 (2 μm) 1.1 balance 20 1.46 0.99 20.4 balance 176 — 37 1.8 (18 μm) 1.1 balance 20 1.77 1.05 19.8 balance 197 — 38 2.1 (2 μm) 1.1 balance 20 2.09 1.07 20.0 balance 189 — 39 2.5 (18 μm) 1.1 balance 20 2.45 1.07 19.7 balance 160 — 40 3.0 (30 μm) 1.2 balance 20 2.96 1.15 19.9 balance 152 — Comparative 7 0.02* (40 μm*) 1.1 balance 20  0.01* 1.04 20.3 balance 23 — products 8 3.5* (0.01 μm*) 1.1 balance 20  3.45* 1.06 19.6 balance 112 decrease in strength Conventional 10 CaMgSi₄:1 (10 μm) 1.1 balance 20 CaMgSi₄:1 1.04 19.8 balance 41 — products 11 MnS:1 (20 μm) 1.1 balance 20 MnS:0.97 1.04 19.8 balance 48 — 12 CaF₂:1 (36 μm) 1.1 balance 20 CaF₂:1 1.04 19.9 balance 32 — The symbol * means the value which is not within the scope of the present invention.

As is apparent from the results shown in Table 4, the number of piercing of the cylindrical sintered alloy blocks for piercing test made of the sintered alloys 31 to 40 of the present invention is larger than that of the cylindrical sintered alloy blocks for piercing test made of the conventional sintered alloys 10 to 12 and therefore the sintered alloys of the present invention are excellent in machinability. However, the comparative sintered alloy 7 containing CaCO₃ in the content of less than the range defined in the present invention is inferior in machinability because of small number of piercing, while the comparative sintered alloy 8 containing CaCO₃ in the content of more than the range defined in the present invention is excellent in machinability because of large number of piercing, but shows drastically decreased deflection strength, and therefore it is not preferred.

EXAMPLE 5

As raw powders, a CaCO₃ powder having an average particle size shown in Table 5, a CaMgSiO₄ powder having an average particle size of 10 μm, a MnS powder having an average particle size of 20 μm, a CaF₂ powder having an average particle size of 36 μm, a Fe powder having an average particle size of 80 μm, a Cu powder having an average particle size of 25 μm and a C powder having an average particle size of 18 μm were prepared. These raw powders were blended according to the formulation shown in Table 5, mixed in a double corn mixer and compacted to obtain a green compact, and then the resulting green compact was sintered in an endothermic gas (ratio of components=H₂: 40.5%, CO: 19.8%, CO₂: 0.1%, CH: 0.5%, and N₂: 39.1%) atmosphere under the conditions of a temperature of 1120° C. and a retention time of 20 minutes to obtain iron-based sintered alloys 41 to 50 of the present invention, comparative sintered alloys 9 to 10, and conventional sintered alloys 13 to 15.

Cylindrical sintered alloy blocks for piercing test each having a diameter of 30 mm and a height of 10 mm, made of the sintered alloys 41 to 50 of the present invention, the comparative sintered alloys 9 to 10, and the conventional sintered alloys 13 to 15 were produced and these cylindrical sintered alloy blocks for piercing test were repeatedly pierced until the drill is damaged, using a high-speed steel drill having a diameter of 1.2 mm, under the following conditions:

-   Rotating speed: 10000 rpm -   Feed speed: 0.030 mm/rev. -   Cutting oil: none (dry).

The number of piercing (maximum number of piercing, lifetime) of one new drill was measured. The results are shown in Table 5. Machinability was evaluated by the results. TABLE 5 Component ratio Component ratio of of raw powder iron-based sintered (mass %) alloy (mass %) CaCO₃ powder Fe Number Average particle and of Iron-based sintered size is described Cu C Fe inevitable piercing alloy in parenthesis. powder powder powder CaCO₃ Cu C impurities (times) Remarks Products of the 41  0.05 (0.1 μm) 0.2 0.13 balance 0.03 2.0 0.11 balance 53 — present 42  0.2 (0.1 μm) 2 0.25 balance 0.17 2.1 0.22 balance 122 — invention 43  0.5 (0.6 μm) 2 0.98 balance 0.47 1.9 0.87 balance 129 — 44  1.0 (2 μm) 2 0.7 balance 0.94 2.0 0.66 balance 235 — 45  1.3 (0.6 μm) 2 0.7 balance 1.22 2.0 0.64 balance 250 — 46  1.5 (2 μm) 4 0.7 balance 1.43 4.0 0.65 balance 220 — 47  1.8 (18 μm) 5.8 0.7 balance 1.69 5.7 0.65 balance 203 — 48  2.1 (2 μm) 4 0.7 balance 2.09 3.9 0.64 balance 190 — 49  2.5 (18 μm) 2 0.98 balance 2.3  2.0 0.88 balance 145 — 50  3.0 (30 μm) 2 1.2 balance 2.91 2.0 1.15 balance 179 — Comparative 9 0.02* (40 μm*) 2 0.7 balance  0.01* 1.9 0.65 balance 10 — products 10  3.5* (0.01 μm*) 2 0.7 balance  3.45* 2.0 0.64 balance 108 decrease in strength Conventional 13 CaMgSi₄:1 2 0.7 balance CaMgSi₄:1 2.0 0.66 balance 20 — products 14 MnS:1 2 0.7 balance MnS:0.97 2.0 0.64 balance 14 — 15 CaF₂:1 2 0.7 balance CaF₂:1 2.0 0.64 balance 9 — The symbol * means the value which is not within the scope of the present invention.

As is apparent from the results shown in Table 5, the number of piercing of the cylindrical sintered alloy blocks for piercing test made of the sintered alloys 41 to 50 of the present invention is larger than that of the cylindrical sintered alloy blocks for piercing test made of the conventional sintered alloys 13 to 15 and therefore the sintered alloys of the present invention are excellent in machinability. However, the comparative sintered alloy 9 containing CaCO₃ in the content of less than the range defined in the present invention is inferior in machinability because of small number of piercing, while the comparative sintered alloy 10 containing CaCO₃ in the content of more than the range defined in the present invention is excellent in machinability because of large number of piercing, but shows drastically decreased deflection strength, and therefore it is not preferred.

EXAMPLE 6

As raw powders, a CaCO₃ powder having an average particle size shown in Table 6, a CaMgSiO₄ powder having an average particle size of 10 μm, a MnS powder having an average particle size of 20 μm, a CaF₂ powder having an average particle size of 36 μm, a partially diffused Fe-based alloy powder having an average particle size of 80 μm with the composition of Fe-1.5% Cu-4.0% Ni-0.5% Mo and a C powder having an average particle size of 18 μm were prepared. These raw powders were blended according to the formulation shown in Table 6, mixed in a double corn mixer and compacted to obtain a green compact, and then the resulting green compact was sintered in an endothermic gas (ratio of components=H₂: 40.5%, CO: 19.8%, CO₂: 0.1%, CH: 0.5%, and N₂: 39.1%) atmosphere under the conditions of a temperature of 1120° C. and a retention time of 20 minutes to obtain iron-based sintered alloys 51 to 60 of the present invention, comparative sintered alloys 11 to 12, and conventional sintered alloys 16 to 18.

Cylindrical sintered alloy blocks for piercing test each having a diameter of 30 mm and a height of 10 mm, made of the sintered alloys 51 to 60 of the present invention, the comparative sintered alloys 11 to 12, and the conventional sintered alloys 16 to 18 were produced and these cylindrical sintered alloy blocks for piercing test were repeatedly pierced until the drill is damaged, using a high-speed steel drill having a diameter of 1.2 mm, under the following conditions:

-   Rotating speed: 5000 rpm -   Feed speed: 0.006 mm/rev. -   Cutting oil: none (dry).

The number of piercing (maximum number of piercing, lifetime) of one new drill was measured. The results are shown in Table 6. Machinability was evaluated by the results. TABLE 6 Component ratio Component ratio of raw powder (mass %) of iron-based sintered alloy (mass %) CaCO₃ powder Fe Number Average particle Fe-based and of Iron-based size is described C alloy inevitable piercing sintered alloy in parenthesis. powder powder# CaCO₃ Cu C Ni Mo impurities (times) Remarks Products of the 51  0.05 (0.1 μm) 0.13 balance 0.03 1.5 0.11 3.9 0.50 balance 48 — present 52  0.2 (0.1 μm) 0.25 balance 0.18 1.5 0.19 4.0 0.50 balance 153 — invention 53  0.5 (0.6 μm) 0.98 balance 0.46 1.5 0.85 4.0 0.50 balance 214 — 54  1.0 (2 μm) 0.5 balance 0.96 1.4 0.47 4.1 0.52 balance 300 — 55  1.3 (0.6 μm) 0.5 balance 1.25 1.5 0.45 4.0 0.50 balance 287 — 56  1.5 (2 μm) 0.5 balance 1.45 1.5 0.45 4.0 0.50 balance 324 — 57  1.8 (18 μm) 0.5 balance 1.72 1.5 0.47 4.0 0.49 balance 274 — 58  2.1 (2 μm) 0.5 balance 1.89 1.6 0.47 3.8 0.50 balance 257 — 59  2.5 (18 μm) 1.0 balance 2.32 1.5 0.90 4.0 0.50 balance 231 — 60  3.0 (30 μm) 1.2 balance 2.89 1.5 1.17 4.0 0.50 balance 267 — Comparative 11 0.02* (40 μm*) 0.5 balance  0.01* 1.5 0.43 4.1 0.50 balance 5 — products 12  3.5* (0.01 μm*) 0.5 balance  3.45* 1.5 0.44 4.0 0.51 balance 87 decrease in strength Conventional 16 CaMgSi₄:1 0.5 balance CaMgSi₄:1 1.5 0.46 4.0 0.50 balance 17 — products 17 MnS:1 0.5 balance MnS:0.97 1.5 0.47 4.0 0.50 balance 35 — 18 CaF₂:1 0.5 balance CaF₂:1 1.5 0.45 4.0 0.48 balance 8 — The symbol * means the value which is not within the scope of the present invention. #partially diffused Fe-based alloy powder having an average particle size of 80 μm with the composition of Fe—1.5% Cu—4.0% Ni-0.5% Mo

As is apparent from the results shown in Table 6, the number of piercing of the cylindrical sintered alloy blocks for piercing test made of the sintered alloys 51 to 60 of the present invention is larger than that of the cylindrical sintered alloy blocks for piercing test made of the conventional sintered alloys 16 to 18 and therefore the sintered alloys of the present invention are excellent in machinability. However, the comparative sintered alloy 11 containing CaCO₃ in the content of less than the range defined in the present invention is inferior in machinability because of small number of piercing, while the comparative sintered alloy 12 containing CaCO₃ in the content of more than the range defined in the present invention is excellent in machinability because of large number of piercing, but shows drastically decreased deflection strength, and therefore it is not preferred.

EXAMPLE 7

As raw powders, a CaCO₃ powder having an average particle size shown in Table 7, a CaMgSiO₄ powder having an average particle size of 10 μm, a MnS powder having an average particle size of 20 μm, a CaF₂ powder having an average particle size of 36 μm, a Fe-based alloy powder having an average particle size of 80 μm with the composition of Fe-1.5% Mo and a C powder having an average particle size of 18 μm were prepared. These raw powders were blended according to the formulation shown in Table 7, mixed in a double corn mixer and compacted to obtain a green compact, and then the resulting green compact was sintered in an endothermic gas (ratio of components=H₂: 40.5%, CO: 19.8%, CO₂: 0.1%, CH: 0.5%, and N₂: 39.1%) atmosphere under the conditions of a temperature of 1120° C. and a retention time of 20 minutes to obtain iron-based sintered alloys 61 to 70 of the present invention, comparative sintered alloys 13 to 14, and conventional sintered alloys 19 to 21.

Cylindrical sintered alloy blocks for piercing test each having a diameter of 30 mm and a height of 10 mm, made of the sintered alloys 61 to 70 of the present invention, the comparative sintered alloys 13 to 14, and the conventional sintered alloys 19 to 21 were produced and these cylindrical sintered alloy blocks for piercing test were repeatedly pierced until the drill is damaged, using a high-speed steel drill having a diameter of 1.2 mm, under the following conditions:

-   Rotating speed: 5000 rpm -   Feed speed: 0.006 mm/rev. -   Cutting oil: none (dry).

The number of piercing (maximum number of piercing, lifetime) of one new drill was measured. The results are shown in Table 7. Machinability was evaluated by the results. TABLE 7 Component ratio Component ratio of iron-based of raw powder (mass %) sintered alloy (mass %) CaCO₃ powder Fe Number Average particle Fe-based and of Iron-based sintered size is described C alloy inevitable piercing alloy in parenthesis. powder powder# CaCO₃ C Mo impurities (times) Remarks Products of the 61  0.05 (0.1 μm) 0.13 balance 0.03 0.11 1.50 balance 48 — present invention 62  0.2 (0.1 μm) 0.25 balance 0.19 0.19 1.48 balance 85 — 63  0.5 (0.6 μm) 0.98 balance 0.48 0.85 1.50 balance 71 — 64  1.0 (2 μm) 0.5 balance 0.97 0.46 1.50 balance 214 — 65  1.3 (0.6 μm) 0.5 balance 1.27 0.47 1.50 balance 225 — 66  1.5 (2 μm) 0.5 balance 1.44 0.45 1.51 balance 201 — 67  1.8 (18 μm) 0.5 balance 1.72 0.45 1.46 balance 228 — 68  2.1 (2 μm) 0.5 balance 1.95 0.44 1.50 balance 219 — 69  2.5 (18 μm) 1.0 balance 2.39 0.90 1.50 balance 170 — 70  3.0 (30 μm) 1.2 balance 2.91 1.17 1.53 balance 148 — Comparative 13 0.02* (40 μm*) 0.5 balance  0.01* 0.43 1.51 balance 12 — products 14  3.5* (0.01 μm*) 0.5 balance  3.45* 0.44 1.50 balance 81 decrease in strength Conventional 19 CaMgSi₄:1 0.5 balance CaMgSi₄:1 0.46 1.51 balance 20 — products 20 MnS:1 0.5 balance MnS:0.97 0.47 1.50 balance 23 — 21 CaF₂:1 0.5 balance CaF₂:1 0.44 1.48 balance 16 — The symbol * means the value which is not within the scope of the present invention. #Fe-based alloy powder having an average particle size of 80 μm with the composition of Fe-1.5% Mo

As is apparent from the results shown in Table 7, the number of piercing of the cylindrical sintered alloy blocks for piercing test made of the sintered alloys 61 to 70 of the present invention is larger than that of the cylindrical sintered alloy blocks for piercing test made of the conventional sintered alloys 19 to 21 and therefore the sintered alloys of the present invention are excellent in machinability. However, the comparative sintered alloy 13 containing CaCO₃ in the content of less than the range defined in the present invention is inferior in machinability because of small number of piercing, while the comparative sintered alloy 14 containing CaCO₃ in the content of more than the range defined in the present invention is excellent in machinability because of large number of piercing, but shows drastically decreased deflection strength, and therefore it is not preferred.

EXAMPLE 8

As raw powders, a CaCO₃ powder having an average particle size shown in Table 8, a CaMgSiO₄ powder having an average particle size of 10 μm, a MnS powder having an average particle size of 20 μm, a CaF₂ powder having an average particle size of 36 μm, a Fe-based alloy powder having an average particle size of 80 μm with the composition of Fe-3.0% Cr-0.5% Mo and a C powder having an average particle size of 18 μm were prepared. These raw powders were blended according to the formulation shown in Table 8, mixed in a double corn mixer and compacted to obtain a green compact, and then the resulting green compact was sintered in an N₂+5% H₂ gas mixture atmosphere under the conditions of a temperature of 1120° C. and a retention time of 20 minutes to obtain iron-based sintered alloys 71 to 80 of the present invention, comparative sintered alloys 15 to 16, and conventional sintered alloys 22 to 24.

Cylindrical sintered alloy blocks for piercing test each having a diameter of 30 mm and a height of 10 mm, made of the sintered alloys 71 to 80 of the present invention, the comparative sintered alloys 15 to 16, and the conventional sintered alloys 22 to 24 were produced and these cylindrical sintered alloy blocks for piercing test were repeatedly pierced until the drill is damaged, using a high-speed steel drill having a diameter of 1.2 mm, under the following conditions:

-   Rotating speed: 10000 rpm -   Feed speed: 0.006 mm/rev. -   Cutting oil: none (dry).

The number of piercing (maximum number of piercing, lifetime) of one new drill was measured. The results are shown in Table 8. Machinability was evaluated by the results. TABLE 8 Component ratio Component ratio of iron-based sintered alloy of raw powder (mass %) (mass %) CaCO₃ powder Fe Number Average particle Fe-based and of Iron-based sintered size is described C alloy inevitable piercing alloy in parenthesis. powder powder# CaCO₃ C Cr Mo impurities (times) Remarks Products of the 71  0.05 (0.1 μm) 0.13 balance 0.03 0.11 3.0 0.50 balance 31 — present 72  0.2 (0.1 μm) 0.25 balance 0.19 0.19 3.0 0.50 balance 105 — invention 73  0.5 (0.6 μm) 0.98 balance 0.48 0.85 3.0 0.49 balance 121 — 74  1.0 (2 μm) 0.5 balance 0.97 0.47 3.0 0.50 balance 163 — 75  1.3 (0.6 μm) 0.5 balance 1.27 0.45 2.9 0.50 balance 186 — 76  1.5 (2 μm) 0.5 balance 1.44 0.45 3.0 0.51 balance 151 — 77  1.8 (18 μm) 0.5 balance 1.72 0.44 3.0 0.49 balance 185 — 78  2.1 (2 μm) 0.5 balance 1.95 0.44 3.1 0.50 balance 196 — 79  2.5 (18 μm) 1.0 balance 2.39 0.90 3.0 0.50 balance 103 — 80  3.0 (30 μm) 1.2 balance 2.91 1.17 3.0 0.50 balance 88 — Comparative 15 0.02* (40 μm*) 0.5 balance  0.01* 0.43 3.1 0.50 balance 3 — products 16  3.5* (0.01 μm*) 0.5 balance  3.45* 0.45 3.0 0.51 balance 89 decrease in strength Conventional 22 CaMgSi₄:1 0.5 balance CaMgSi₄:1 0.46 3.0 0.50 balance 16 — products 23 MnS:1 0.5 balance MnS:0.97 0.47 3.1 0.50 balance 13 — 24 CaF₂:1 0.5 balance CaF₂:1 0.44 3.0 0.50 balance 8 — The symbol * means the value which is not within the scope of the present invention. #Fe-based alloy powder having a particle size of 80 μm with the composition of Fe—3.0% Cr—0.5% Mo

As is apparent from the results shown in Table 8, the number of piercing of the cylindrical sintered alloy blocks for piercing test made of the sintered alloys 71 to 80 of the present invention is larger than that of the cylindrical sintered alloy blocks for piercing test made of the conventional sintered alloys 22 to 24 and therefore the sintered alloys of the present invention are excellent in machinability. However, the comparative sintered alloy 15 containing CaCO₃ in the content of less than the range defined in the present invention is inferior in machinability because of small number of piercing, while the comparative sintered alloy 16 containing CaCO₃ in the content of more than the range defined in the present invention is excellent in machinability because of large number of piercing, but shows drastically decreased deflection strength, and therefore it is not preferred.

EXAMPLE 9

As raw powders, a CaCO₃ powder having an average particle size shown in Table 9, a CaMgSiO₄ powder having an average particle size of 10 μm, a MnS powder having an average particle size of 20 μm, a CaF₂ powder having an average particle size of 36 μm, a Fe-based alloy powder having an average particle size of 80 μm with the composition of Fe-3.0% Cr-0.5% Mo, a Ni powder having an average particle size of 3 μm and a C powder having an average particle size of 18 μm were prepared. These raw powders were blended according to the formulation shown in Table 9, mixed in a double corn mixer and compacted to obtain a green compact, and then the resulting green compact was sintered in an N₂+5% H₂ gas mixture atmosphere under the conditions of a temperature of 1120° C. and a retention time of 20 minutes to obtain iron-based sintered alloys 81 to 90 of the present invention, comparative sintered alloys 17 to 18, and conventional sintered alloys 25 to 27.

Cylindrical sintered alloy blocks for piercing test each having a diameter of 30 mm and a height of 10 mm, made of the sintered alloys 81 to 90 of the present invention, the comparative sintered alloys 17 to 18, and the conventional sintered alloys 25 to 27 were produced and these cylindrical sintered alloy blocks for piercing test were repeatedly pierced until the drill is damaged, using a high-speed steel drill having a diameter of 1.2 mm, under the following conditions:

-   Rotating speed: 5000 rpm -   Feed speed: 0.006 mm/rev. -   Cutting oil: none (dry).

The number of piercing (maximum number of piercing, lifetime) of one new drill was measured. The results are shown in Table 9. Machinability was evaluated by the results. TABLE 9 Component ratio Component ratio of of raw powder (mass %) iron-based sintered alloy (mass %) CaCO₃ powder Fe Number Average particle Fe-based and of Iron-based size is described alloy inevitable piercing sintered alloy in parenthesis. C powder Ni powder powder# CaCO₃ C Ni Cr Mo impurities (times) Remarks Products of the 81  0.05 (0.1 μm) 0.13 0.2 balance 0.03 0.11 0.2 3.0 0.50 balance 65 — present 82  0.2 (0.1 μm) 0.25 2 balance 0.19 0.19 2.0 3.0 0.50 balance 93 — invention 83  0.5 (0.6 μm) 0.98 4 balance 0.48 0.85 4.0 3.0 0.49 balance 89 — 84  1.0 (2 μm) 0.5 4 balance 0.97 0.47 4.0 3.0 0.50 balance 135 — 85  1.3 (0.6 μm) 0.5 4 balance 1.27 0.45 3.9 2.9 0.50 balance 112 — 86  1.5 (2 μm) 0.5 4 balance 1.44 0.45 4.0 3.0 0.51 balance 125 — 87  1.8 (18 μm) 0.5 4 balance 1.72 0.44 4.0 3.0 0.49 balance 140 — 88  2.1 (2 μm) 0.5 6 balance 1.95 0.44 6.0 3.1 0.50 balance 177 — 89  2.5 (18 μm) 1.0 8 balance 2.39 0.90 7.9 3.0 0.50 balance 133 — 90  3.0 (30 μm) 1.2 9.8 balance 2.91 1.17 9.8 3.0 0.50 balance 109 — Comparative 17 0.02* (40 μm*) 0.5 4 balance  0.01* 0.43 4.1 3.1 0.50 balance 3 — products 18  3.5* (0.01 μm*) 0.5 4 balance  3.45* 0.45 4.0 3.0 0.51 balance 101 decrease in strength Conventional 25 CaMgSi₄:1 0.5 4 balance CaMgSi₄:1 0.46 4.0 3.0 0.50 balance 6 — products 26 MnS:1 0.5 4 balance MnS:0.97 0.47 4.0 3.1 0.50 balance 8 — 27 CaF₂:1 0.5 4 balance CaF₂:1 0.44 4.0 3.0 0.50 balance 8 — The symbol * means the value which is not within the scope of the present invention. #Fe-based alloy powder having a particle size of 80 μm with the composition of Fe—3.0% Cr—0.5% Mo

As is apparent from the results shown in Table 9, the number of piercing of the cylindrical sintered alloy blocks for piercing test made of the sintered alloys 81 to 90 of the present invention is larger than that of the cylindrical sintered alloy blocks for piercing test made of the conventional sintered alloys 25 to 27 and therefore the sintered alloys of the present invention are excellent in machinability. However, the comparative sintered alloy 17 containing CaCO₃ in the content of less than the range defined in the present invention is inferior in machinability because of small number of piercing, while the comparative sintered alloy 18 containing CaCO₃ in the content of more than the range defined in the present invention is excellent in machinability because of large number of piercing, but shows drastically decreased deflection strength, and therefore it is not preferred.

EXAMPLE 10

As raw powders, a CaCO₃ powder having an average particle size shown in Table 10, a CaMgSiO₄ powder having an average particle size of 10 μm, a MnS powder having an average particle size of 20 μm, a CaF₂ powder having an average particle size of 36 μm, a Fe-based alloy powder having an average particle size of 80 μm with the composition of Fe-3.0% Cr-0.5% Mo, a Cu powder having an average particle size of 25 μm, a Ni powder having an average particle size of 3 μm and a C powder having an average particle size of 18 μm were prepared. These raw powders were blended according to the formulation shown in Table 10, mixed in a double corn mixer and compacted to obtain a green compact, and then the resulting green compact was sintered in an N₂+5% H₂ gas mixture atmosphere under the conditions of a temperature of 1120° C. and a retention time of 20 minutes to obtain iron-based sintered alloys 91 to 100 of the present invention, comparative sintered alloys 19 to 20, and conventional sintered alloys 28 to 30.

Cylindrical sintered alloy blocks for piercing test each having a diameter of 30 mm and a height of 10 mm, made of the sintered alloys 91 to 100 of the present invention, the comparative sintered alloys 19 to 20, and the conventional sintered alloys 28 to 30 were produced and these cylindrical sintered alloy blocks for piercing test were repeatedly pierced until the drill is damaged, using a high-speed steel drill having a diameter of 1.2 mm, under the following conditions:

-   Rotating speed: 5000 rpm -   Feed speed: 0.006 mm/rev. -   Cutting oil: none (dry).

The number of piercing (maximum number of piercing, lifetime) of one new drill was measured. The results are shown in Table 10. Machinability was evaluated by the results. TABLE 10 Component ratio Component ratio of of raw powder (mass %) iron-based sintered alloy (mass %) CaCO₃ powder Fe Number Average particle Cu Fe- and of Iron-based size is described pow- C Ni based inevitable piercing sintered alloy in parenthesis. der powder powder alloy # CaCO₃ Cu C Ni Cr Mo impurities (times) Remarks Products 91  0.05 (0.1 μm) 0.2 0.13 0.2 balance 0.03 0.2 0.11 0.2 3.0 0.50 balance 34 — of the 92  0.2 (0.1 μm) 2 0.25 2 balance 0.19 2.1 0.19 2.0 3.0 0.50 balance 87 — present 93  0.5 (0.6 μm) 2 0.98 4 balance 0.48 1.9 0.85 4.0 3.0 0.49 balance 95 — invention 94  1.0 (2 μm) 2 0.5 4 balance 0.97 2.0 0.47 4.0 3.0 0.50 balance 150 — 95  1.3 (0.6 μm) 2 0.5 4 balance 1.27 2.0 0.45 3.9 2.9 0.50 balance 138 — 96  1.5 (2 μm) 4 0.5 4 balance 1.44 4.0 0.45 4.0 3.0 0.51 balance 143 — 97  1.8 (18 μm) 5.8 0.5 4 balance 1.72 5.8 0.44 4.0 3.0 0.49 balance 139 — 98  2.1 (2 μm) 4 0.5 6 balance 1.95 4.0 0.44 6.0 3.1 0.50 balance 155 — 99  2.5 (18 μm) 2 1.0 8 balance 2.39 2.0 0.90 7.9 3.0 0.50 balance 132 — 100  3.0 (30 μm) 2 1.2 9.8 balance 2.91 2.0 1.17 9.8 3.0 0.50 balance 129 — Com- 19 0.02* (40 μm*) 2 0.5 4 balance  0.01* 1.9 0.43 4.1 3.0 0.50 balance 2 — parative products 20  3.5* (0.01 μm*) 2 0.5 4 balance  3.45* 2.0 0.45 4.0 3.0 0.51 balance 119 decrease in strength Con- 28 CaMgSi₄:1 2 0.5 4 balance CaMgSi₄:1 2.0 0.46 4.0 3.0 0.50 balance 8 — ventional 29 MnS:1 2 0.5 4 balance MnS:0.97 2.0 0.47 4.0 3.1 0.50 balance 4 — products 30 CaF₂:1 2 0.5 4 balance CaF₂:1 2.0 0.44 4.0 3.0 0.50 balance 11 — The symbol * means the value which is not within the scope of the present invention. *Fe-based alloy powder having a particle size of 80 μm with the composition of Fe—3.0% Cr—0.5% Mo

As is apparent from the results shown in Table 10, the number of piercing of the cylindrical sintered alloy blocks for piercing test made of the sintered alloys 91 to 100 of the present invention is larger than that of the cylindrical sintered alloy blocks for piercing test made of the conventional sintered alloys 28 to 30 and therefore the sintered alloys of the present invention are excellent in machinability. However, the comparative sintered alloy 19 containing CaCO₃ in the content of less than the range defined in the present invention is inferior in machinability because of small number of piercing, while the comparative sintered alloy 20 containing CaCO₃ in the content of more than the range defined in the present invention is excellent in machinability because of large number of piercing, but shows drastically decreased deflection strength, and therefore it is not preferred.

EXAMPLE 11

As raw powders, a CaCO₃ powder having an average particle size shown in Table 11, a CaMgSiO₄ powder having an average particle size of 10 μm, a MnS powder having an average particle size of 20 μm, a CaF₂ powder having an average particle size of 36 μm, a Fe powder having an average particle size of 80 μm, a Ni powder having an average particle size of 3 μm and a C powder having an average particle size of 18 μm were prepared. These raw powders were blended according to the formulation shown in Table 11, mixed in a double corn mixer and compacted to obtain a green compact, and then the resulting green compact was sintered in an endothermic gas (ratio of components=H₂: 40.5%, CO: 19.8%, CO₂: 0.1%, CH: 0.5%, and N₂: 39.1%) atmosphere under the conditions of a temperature of 1120° C. and a retention time of 20 minutes to obtain iron-based sintered alloys 101 to 110 of the present invention, comparative sintered alloys 21 to 22, and conventional sintered alloys 31 to 33.

Cylindrical sintered alloy blocks for piercing test each having a diameter of 30 mm and a height of 10 mm, made of the sintered alloys 101 to 110 of the present invention, the comparative sintered alloys 21 to 22, and the conventional sintered alloys 31 to 33 were produced and these cylindrical sintered alloy blocks for piercing test were repeatedly pierced until the drill is damaged, using a high-speed steel drill having a diameter of 1.2 mm, under the following conditions:

-   Rotating speed: 5000 rpm -   Feed speed: 0.009 mm/rev. -   Cutting oil: none (dry).

The number of piercing (maximum number of piercing, lifetime) of one new drill was measured. The results are shown in Table 11. Machinability was evaluated by the results. TABLE 11 Component ratio of raw powder (mass %) Component ratio of iron-based CaCO₃ powder sintered alloy (mass %) Average particle Fe and Number of Iron-based sintered size is described C Ni Fe inevitable piercing alloy in parenthesis. powder powder powder CaCO₃ C Ni impurities (times) Remarks Products of 101  0.05 (0.1 μm) 0.13 0.2 balance 0.03 0.11 0.2 balance 43 — the present 102  0.2 (0.1 μm) 0.25 1 balance 0.19 0.19 1.0 balance 84 — invention 103  0.5 (0.6 μm) 0.98 3 balance 0.48 0.93 2.9 balance 79 — 104  1.0 (2 μm) 0.5 3 balance 0.97 0.44 3.0 balance 128 — 105  1.3 (0.6 μm) 0.5 3 balance 1.27 0.44 3.0 balance 114 — 106  1.5 (2 μm) 0.5 3 balance 1.44 0.45 3.0 balance 202 — 107  1.8 (18 μm) 0.5 3 balance 1.72 0.45 3.0 balance 187 — 108  2.1 (2 μm) 0.5 6 balance 1.95 0.45 6.0 balance 168 — 109  2.5 (18 μm) 1.0 8 balance 2.39 0.90 8.0 balance 126 — 110  3.0 (30 μm) 1.2 9.8 balance 2.91 1.11 9.8 balance 99 — Comparative 21 0.02* (40 μm*) 0.5 3 balance 0.01* 0.45 3.0 balance 5 — products 22  3.5* (0.01 μm*) 0.5 3 balance 3.45* 0.45 3.0 balance 143 decrease in strength Conventional 31 CaMgSi₄:1 0.5 3 balance CaMgSi₄:1 0.44 2.9 balance 17 — products 32 MnS:1 0.5 4 balance MnS:0.97 0.45 3.0 balance 20 — 33 CaF₂:1 0.5 4 balance CaF₂:1 0.44 3.0 balance 12 — The symbol * means the value which is not within the scope of the present invention.

As is apparent from the results shown in Table 11, the number of piercing of the cylindrical sintered alloy blocks for piercing test made of the sintered alloys 101 to 110 of the present invention is larger than that of the cylindrical sintered alloy blocks for piercing test made of the conventional sintered alloys 31 to 33 and therefore the sintered alloys of the present invention are excellent in machinability. However, the comparative sintered alloy 21 containing CaCO₃ in the content of less than the range defined in the present invention is inferior in machinability because of small number of piercing, while the comparative sintered alloy 22 containing CaCO₃ in the content of more than the range defined in the present invention is excellent in machinability because of large number of piercing, but shows drastically decreased deflection strength, and therefore it is not preferred.

EXAMPLE 12

As raw powders, a CaCO₃ powder having an average particle size shown in Table 12, a CaMgSiO₄ powder having an average particle size of 10 μm, a MnS powder having an average particle size of 20 μm, a CaF₂ powder having an average particle size of 36 μm, a Fe powder having an average particle size of 80 μm, a Ni powder having an average particle size of 3 μm, a Mo powder having an average particle size of 3 μm and a C powder having an average particle size of 18 μm were prepared. These raw powders were blended according to the formulation shown in Table 12, mixed in a double corn mixer and compacted to obtain a green compact, and then the resulting green compact was sintered in an endothermic gas (ratio of components=H₂: 40.5%, CO: 19.8%, CO₂: 0.1%, CH: 0.5%, and N₂: 39.1%) atmosphere under the conditions of a temperature of 1120° C. and a retention time of 20 minutes to obtain iron-based sintered alloys 111 to 120 of the present invention, comparative sintered alloys 23 to 24, and conventional sintered alloys 34 to 36.

Cylindrical sintered alloy blocks for piercing test each having a diameter of 30 mm and a height of 10 mm, made of the sintered alloys 111 to 120 of the present invention, the comparative sintered alloys 23 to 24, and the conventional sintered alloys 34 to 36 were produced and these cylindrical sintered alloy blocks for piercing test were repeatedly pierced until the drill is damaged, using a high-speed steel drill having a diameter of 1.2 mm, under the following conditions:

-   Rotating speed: 5000 rpm -   Feed speed: 0.009 mm/rev. -   Cutting oil: none (dry).

The number of piercing (maximum number of piercing, lifetime) of one new drill was measured. The results are shown in Table 12. Machinability was evaluated by the results. TABLE 12 Component ratio of raw powder (mass %) CaCO₃ powder Component ratio of iron-based sintered alloy Average (mass %) Number particle size is Fe and of Iron-based sintered described in C Ni Mo Fe inevitable piercing alloy parenthesis. powder powder powder powder CaCO₃ C Ni Mo impurities (times) Remarks Products of the 111  0.05 (0.1 μm) 0.13 0.2 0.2 balance 0.03 0.11 0.2 0.2 balance 55 — present 112  0.2 (0.1 μm) 0.25 1 0.3 balance 0.19 0.19 1.0 0.3 balance 91 — invention 113  0.5 (0.6 μm) 0.98 4 0.5 balance 0.48 0.91 4.0 0.5 balance 103 — 114  1.0 (2 μm) 0.6 4 0.5 balance 0.97 0.55 4.0 0.5 balance 170 — 115  1.3 (0.6 μm) 0.6 4 0.5 balance 1.27 0.56 4.0 0.5 balance 227 — 116  1.5 (2 μm) 0.6 4 1 balance 1.44 0.54 3.9 1.0 balance 198 — 117  1.8 (18 μm) 0.6 4 3 balance 1.72 0.54 3.9 2.7 balance 164 — 118  2.1 (2 μm) 0.6 6 4.8 balance 1.95 0.55 6.0 4.8 balance 144 — 119  2.5 (18 μm) 1.0 8 0.5 balance 2.39 0.92 8.0 0.5 balance 159 — 120  3.0 (30 μm) 1.2 9.8 0.5 balance 2.91 1.14 9.8 0.5 balance 166 — Comparative 23 0.02* (40 μm*) 0.6 4 0.5 balance 0.01* 0.54 4.0 0.5 balance 11 — products 24  3.5* (0.01 μm*) 0.6 4 0.5 balance 3.45* 0.54 4.0 0.5 balance 91 decrease in strength Conventional 34 CaMgSi₄:1 0.6 4 0.5 balance CaMgSi₄:1 0.54 4.0 0.5 balance 22 — products 35 MnS:1 0.6 4 0.5 balance MnS:0.97 0.55 4.0 0.5 balance 31 — 36 CaF₂:1 0.6 4 0.5 balance CaF₂:1 0.55 4.0 0.5 balance 28 — The symbol * means the value which is not within the scope of the present invention.

As is apparent from the results shown in Table 12, the number of piercing of the cylindrical sintered alloy blocks for piercing test made of the sintered alloys 111 to 120 of the present invention is larger than that of the cylindrical sintered alloy blocks for piercing test made of the conventional sintered alloys 34 to 36 and therefore the sintered alloys of the present invention are excellent in machinability. However, the comparative sintered alloy 23 containing CaCO₃ in the content of less than the range defined in the present invention is inferior in machinability because of small number of piercing, while the comparative sintered alloy 24 containing CaCO₃ in the content of more than the range defined in the present invention is excellent in machinability because of large number of piercing, but shows drastically decreased deflection strength, and therefore it is not preferred.

EXAMPLE 13

As raw powders, a CaCO₃ powder having an average particle size shown in Table 13, a CaMgSiO₄ powder having an average particle size of 10 μm, a MnS powder having an average particle size of 20 μm, a CaF₂ powder having an average particle size of 36 μm, a Fe powder having an average particle size of 80 μm, a Ni powder having an average particle size of 3 μm, a Cu powder having an average particle size of 25 μm and a C powder having an average particle size of 18 μm were prepared. These raw powders were blended according to the formulation shown in Table 13, mixed in a double corn mixer and compacted to obtain a green compact, and then the resulting green compact was sintered in an endothermic gas (ratio of components=H₂: 40.5%, CO: 19.8%, CO₂: 0.1%, CH: 0.5%, and N₂: 39.1%) atmosphere under the conditions of a temperature of 1120° C. and a retention time of 20 minutes to obtain iron-based sintered alloys 121 to 130 of the present invention, comparative sintered alloys 25 to 26, and conventional sintered alloys 37 to 39.

Cylindrical sintered alloy blocks for piercing test each having a diameter of 30 mm and a height of 10 mm, made of the sintered alloys 121 to 130 of the present invention, the comparative sintered alloys 25 to 26, and the conventional sintered alloys 37 to 39 were produced and these cylindrical sintered alloy blocks for piercing test were repeatedly pierced until the drill is damaged, using a high-speed steel drill having a diameter of 1.2 mm, under the following conditions:

-   Rotating speed: 5000 rpm -   Feed speed: 0.009 mm/rev. -   Cutting oil: none (dry).

The number of piercing (maximum number of piercing, lifetime) of one new drill was measured. The results are shown in Table 13. Machinability was evaluated by the results. TABLE 13 Component ratio of raw powder (mass %) CaCO₃ powder Component ratio of iron-based sintered alloy Average (mass %) Number particle size is Fe and of Iron-based sintered described in Cu C Ni Fe inevitable piercing alloy parenthesis. powder powder powder powder CaCO₃ Cu C Ni impurities (times) Remarks Products of the 121  0.05 (0.1 μm) 0.2 0.13 0.2 balance 0.03 0.2 0.11 0.2 balance 46 — present 122  0.2 (0.1 μm) 1 0.25 1 balance 0.17 1.0 0.21 1.0 balance 104 — invention 123  0.5 (0.6 μm) 1 0.98 3 balance 0.47 1.0 0.91 3.0 balance 136 — 124  1.0 (2 μm) 1 0.6 3 balance 0.94 0.99 0.55 3.0 balance 157 — 125  1.3 (0.6 μm) 2 0.8 3 balance 1.22 1.0 0.54 3.0 balance 180 — 126  1.5 (2 μm) 4 0.6 3 balance 1.43 4.0 0.55 2.9 balance 166 — 127  1.8 (18 μm) 5.8 0.6 3 balance 1.69 5.7 0.56 3.0 balance 192 — 128  2.1 (2 μm) 1 0.6 6 balance 1.09 1.0 0.55 6.0 balance 153 — 129  2.5 (18 μm) 1 1.0 8 balance 2.3 1.0 0.91 8.0 balance 193 — 130  3.0 (30 μm) 1 1.2 9.8 balance 2.91 1.0 1.13 9.8 balance 179 — Comparative 25 0.02* (40 μm*) 1 0.6 3 balance 0.01* 1.0 0.55 3.0 balance 7 — products 26  3.5* (0.01 μm*) 1 0.6 3 balance 3.45* 1.0 0.55 3.0 balance 79 decrease in strength Conventional 37 CaMgSi₄:1 1 0.6 3 balance CaMgSi₄:1 1.0 0.55 3.0 balance 12 — products 38 MnS:1 1 0.6 3 balance MnS:0.97 1.0 0.54 3.0 balance 15 — 39 CaF₂:1 1 0.6 3 balance CaF₂:1 1.0 0.55 3.0 balance 9 — The symbol * means the value which is not within the scope of the present invention.

As is apparent from the results shown in Table 13, the number of piercing of the cylindrical sintered alloy blocks for piercing test made of the sintered alloys 121 to 130 of the present invention is larger than that of the cylindrical sintered alloy blocks for piercing test made of the conventional sintered alloys 37 to 39 and therefore the sintered alloys of the present invention are excellent in machinability. However, the comparative sintered alloy 25 containing CaCO₃ in the content of less than the range defined in the present invention is inferior in machinability because of small number of piercing, while the comparative sintered alloy 26 containing CaCO₃ in the content of more than the range defined in the present invention is excellent in machinability because of large number of piercing, but shows drastically decreased deflection strength, and therefore it is not preferred.

EXAMPLE 14

As raw powders, a CaCO₃ powder having an average particle size shown in Table 14, a CaMgSiO₄ powder having an average particle size of 10 μm, a MnS powder having an average particle size of 20 μm, a CaF₂ powder having an average particle size of 36 μm, a Fe powder having an average particle size of 80 μm, a Cu—P powder having an average particle size of 25 μm and a C powder having an average particle size of 18 μm were prepared. These raw powders were blended according to the formulation shown in Table 14, mixed in a double corn mixer and compacted to obtain a green compact, and then the resulting green compact was sintered in an endothermic gas (ratio of components=H₂: 40.5%, CO: 19.8%, CO₂: 0.1%, CH: 0.5%, and N₂: 39.1%) atmosphere under the conditions of a temperature of 1120° C. and a retention time of 20 minutes to obtain iron-based sintered alloys 131 to 140 of the present invention, comparative sintered alloys 27 to 28, and conventional sintered alloys 40 to 42.

Cylindrical sintered alloy blocks for piercing test each having a diameter of 30 mm and a height of 10 mm, made of the sintered alloys 131 to 140 of the present invention, the comparative sintered alloys 27 to 28, and the conventional sintered alloys 40 to 42 were produced and these cylindrical sintered alloy blocks for piercing test were repeatedly pierced until the drill is damaged, using a high-speed steel drill having a diameter of 1.2 mm, under the following conditions:

-   Rotating speed: 10000 rpm -   Feed speed: 0.009 mm/rev. -   Cutting oil: none (dry).

The number of piercing (maximum number of piercing, lifetime) of one new drill was measured. The results are shown in Table 14. Machinability was evaluated by the results. TABLE 14 Component ratio of iron-based Component ratio of raw powder (mass %) sintered alloy CaCO₃ powder (mass %) Number Average particle Fe and of Iron-based sintered size is described C Cu—P Fe inevitable piercing alloy in parenthesis. powder powder powder CaCO₃ C Cu P impurities (times) Remarks Products 131  0.05 (0.1 μm) 1.0 0.7 balance 0.03 0.91 0.6 0.1 balance 77 — of the 132  0.2 (0.1 μm) 1.5 1.2 balance 0.19 1.44 1.1 0.1 balance 73 — present 133  0.5 (0.6 μm) 1.5 1.8 balance 0.48 1.46 1.6 0.2 balance 114 — invention 134  1.0 (2 μm) 2.0 1.8 balance 0.97 1.95 1.6 0.2 balance 203 — 135  1.3 (0.6 μm) 2.0 2.8 balance 1.27 1.93 2.5 0.3 balance 231 — 136  1.5 (2 μm) 2.0 2.8 balance 1.44 1.93 2.5 0.3 balance 211 — 137  1.8 (18 μm) 2.0 3.3 balance 1.72 1.96 3 0.3 balance 274 — 138  2.1 (2 μm) 2.5 6.0 balance 1.95 2.48 5.4 0.6 balance 177 — 139  2.5 (18 μm) 2.5 8.0 balance 2.39 2.45 5 0.6 balance 229 — 140  3.0 (30 μm) 3.0 9.0 balance 2.91 2.99 8.2 0.8 balance 310 — Comparative 27 0.02* (40 μm*) 1 2.8 balance 0.01* 0.45 2.5 0.3 balance 2 — products 28  3.5* (0.01 μm*) 1 2.8 balance 3.43* 0.45 2.5 0.3 balance 198 decrease in strength Conventional 40 CaMgSi₄:1 1 2.8 balance CaMgSi₄:1 0.44 2.9 0.3 balance 32 — products 41 MnS:1 1 2.8 balance MnS:0.97 0.45 3.0 0.3 balance 53 — 42 CaF₂:1 1 2.8 balance CaF₂:1 0.44 3.0 0.3 balance 40 — The symbol * means the value which is not within the scope of the present invention.

As is apparent from the results shown in Table 14, the number of piercing of the cylindrical sintered alloy blocks for piercing test made of the sintered alloys 131 to 140 of the present invention is larger than that of the cylindrical sintered alloy blocks for piercing test made of the conventional sintered alloys 40 to 42 and therefore the sintered alloys of the present invention are excellent in machinability. However, the comparative sintered alloy 27 containing CaCO₃ in the content of less than the range defined in the present invention is inferior in machinability because of small number of piercing, while the comparative sintered alloy 28 containing CaCO₃ in the content of more than the range defined in the present invention is excellent in machinability because of large number of piercing, but shows drastically decreased deflection strength, and therefore it is not preferred.

EXAMPLE 15

As raw powders, a CaCO₃ powder having an average particle size of 0.6 μm, a CaF₂ powder having an average particle size of 36 μm and a Fe-6% Cr-6% Mo-9% W-3% V-10% Co-1.5% C powder having an average particle size of 80 μm were prepared. These raw powders were blended according to the formulation shown in Table 15, mixed in a double corn mixer and compacted to obtain a green compact, and then the resulting green compact was sintered in a dissociated ammonia gas atmosphere under the conditions of a temperature of 1150° C. and a retention time of 60 minutes to obtain an iron-based sintered alloy 141 of the present invention, comparative sintered alloys 29 to 30, and a conventional sintered alloy 43.

Cylindrical sintered alloy blocks for piercing test each having a diameter of 30 mm and a height of 10 mm, made of the sintered alloy 141 of the present invention, the comparative sintered alloys 29 to 30, and the conventional sintered alloy 43 were produced and these cylindrical sintered alloy blocks for piercing test were repeatedly pierced until the drill is damaged, using a high-speed steel drill having a diameter of 1.2 mm, under the following conditions:

-   Rotating speed: 5000 rpm -   Feed speed: 0.006 mm/rev. -   Cutting oil: none (dry).

The number of piercing (maximum number of piercing, lifetime) of one new drill was measured. The results are shown in Table 15. Machinability was evaluated by the results. TABLE 15 Component ratio of raw powder (mass %) Fe—6%Cr— CaCO₃ powder 6%Mo— Component ratio Average particle 9%W—3%V— of iron-based sintered alloy (mass %) size 10%Co— Fe and Number of Iron-based sintered is described in 1.5%C inevitable piercing alloy parenthesis. powder CaCO₃ C Cr Mo W Co V impurities (times) Remarks Product of the 141  0.5 (0.6 μm) balance 0.48 1.5 6 6 9 10 3 balance 158 — present invention Comparative 29 0.02* (40 μm*) balance 0.01* 1.5 6 6 9 10 3 balance 18 — products 30  3.5* (0.01 μm*) balance 3.43* 1.5 6 6 9 10 3 balance 127 decrease in strength Conventional 43 CaF₂:1 balance CaF₂:1 1.5 6 6 9 10 3 balance 26 — product The symbol * means the value which is not within the scope of the present invention.

As is apparent from the results shown in Table 15, the number of piercing of the cylindrical sintered alloy block for piercing test made of the sintered alloy 141 of the present invention is larger than that of the cylindrical sintered alloy block for piercing test made of the conventional sintered alloy 43 and therefore the sintered alloy of the present invention is excellent in machinability. However, the comparative sintered alloy 29 containing CaCO₃ in the content of less than the range defined in the present invention is inferior in machinability because of small number of piercing, while the comparative sintered alloy 30 containing CaCO₃ in the content of more than the range defined in the present invention is excellent in machinability because of large number of piercing, but shows drastically decreased deflection strength, and therefore it is not preferred.

EXAMPLE 16

As raw powders, a CaCO₃ powder having an average particle size of 0.6 μm, a CaF₂ powder having an average particle size of 36 μm, a Fe-based alloy powder having an average particle size of 80 μm with the composition of Fe-13% Cr-5% Nb-0.8% Si, a Fe powder having an average particle size of 80 μm, a Ni powder having an average particle size of 3 μm, a Mo powder having an average particle size of 3 μm, a Co-based alloy powder having an average particle size of 80 μm with the composition of Co-30% Mo-10% Cr-3% Si, a Cr-based alloy powder having an average particle size of 80 μm with the composition of Cr-25% Co-25% W-11.5% Fe-1% Nb-1% Si-1.5% C, a Co powder having an average particle size of 30 μm and a C powder having an average particle size of 18 μm were prepared. These raw powders were blended according to the formulation shown in Table 16-1, mixed in a double corn mixer and compacted to obtain a green compact, and then the resulting green compact was sintered in a vacuum atmosphere at 0.1 Pa under the conditions of a temperature of 1150° C. and a retention time of 60 minutes to obtain an iron-based sintered alloy 142 of the present invention, comparative sintered alloys 31 to 32, and a conventional sintered alloy 44 shown in Table 16-2.

Cylindrical sintered alloy blocks for piercing test each having a diameter of 30 mm and a height of 10 mm, made of the sintered alloy 142 of the present invention, the comparative sintered alloys 31 to 32, and the conventional sintered alloy 44 were produced and these cylindrical sintered alloy blocks for piercing test were repeatedly pierced until the drill is damaged, using a high-speed steel drill having a diameter of 1.2 mm, under the following conditions:

-   Rotating speed: 5000 rpm -   Feed speed: 0.006 mm/rev. -   Cutting oil: none (dry).

The number of piercing (maximum number of piercing, lifetime) of one new drill was measured. The results are shown in Table 16-2. Machinability was evaluated by the results. TABLE 16-1 Component ratio of raw powder (mass %) CaCO₃ powder Average particle size is Co-based Cr-based Fe-based Iron-based sintered described in Mo alloy alloy Ni C Co alloy Fe alloy parenthesis. powder powder# powder# powder powder powder powder# powder Product of the 142  0.5 (0.6 μm) 9.0 10 12 3 0.8 3.3 10 balance present invention Comparative 31 0.02* (40 μm*) 9.0 10 12 3 0.8 3.3 10 balance products 32  3.5* (0.01 μm*) 9.0 10 12 3 0.8 3.3 10 balance Conventional 44 CaF₂:1 9.0 10 12 3 0.8 3.3 10 balance product Fe-based alloy powder#: Fe—13%Cr—5%Nb—0.8%Si Co-based alloy powder#: Co—30%Mo—10%Cr—3%Si Cr-based alloy powder#: Cr—25%Co—25%W—11.5%Fe—1%Nb—1%Si—1.5%C The symbol * means the value which is not within the scope of the present invention.

TABLE 16-2 Component ratio of iron-based sintered alloy (mass %) Number of Fe and inevitable piercing Iron-based sintered alloy CaCO₃ C Cr Mo W Ni Si Co Nb impurities (times) Remarks Product of the present 142 0.47 1 6 12 3 3 0.5 11.7 1.1 balance 250 — invention Comparative products 31 0.01* 1 6 12 3 3 0.5 11.7 1.1 balance 14 — 32 3.47* 1 6 12 3 3 0.5 11.7 1.1 balance 140 decrease in strength Conventional 44 CaF₂:1 1 6 12 3 3 0.5 11.7 1.1 balance 31 — product The symbol * means the value which is not within the scope of the present invention.

As is apparent from the results shown in Table 16-1 and Table 16-2, the number of piercing of the cylindrical sintered alloy block for piercing test made of the sintered alloy 142 of the present invention is larger than that of the cylindrical sintered alloy block for piercing test made of the conventional sintered alloy 44 and therefore the sintered alloy of the present invention is excellent in machinability. However, the comparative sintered alloy 31 containing CaCO₃ in the content of less than the range defined in the present invention is inferior in machinability because of small number of piercing, while the comparative sintered alloy 32 containing CaCO₃ in the content of more than the range defined in the present invention is excellent in machinability because of large number of piercing, but shows drastically decreased deflection strength, and therefore it is not preferred.

EXAMPLE 17

As raw powders, a CaCO₃ powder having an average particle size of 0.6 μm, a CaF₂ powder having an average particle size of 36 μm, a Fe-based alloy powder having an average particle size of 80 μm with the composition of Fe-13% Cr-5% Nb-0.8% Si, a Fe powder having an average particle size of 80 μm, a Ni powder having an average particle size of 3 μm, a Mo powder having an average particle size of 3 μm, a Co-based alloy powder having an average particle size of 80 μm with the composition of Co-30% Mo-10% Cr-3% Si, a Cr-based alloy powder having an average particle size of 80 μm with the composition of Cr-25% Co-25% W-11.5% Fe-1% Nb-1% Si-1.5% C, a Co powder having an average particle size of 30 μm and a C powder having an average particle size of 18 μm were prepared. These raw powders were blended according to the formulation shown in Table 17-1, mixed in a double corn mixer and compacted to obtain a green compact, and then the resulting green compact was sintered in a vacuum atmosphere at 0.1 Pa under the conditions of a temperature of 1150° C. and a retention time of 60 minutes and subjected to 18% Cu infiltration to obtain an iron-based sintered alloy 143 of the present invention, comparative sintered alloys 33 to 34, and a conventional sintered alloy 45 shown in Table 17-2.

Cylindrical sintered alloy blocks for piercing test each having a diameter of 30 mm and a height of 10 mm, made of the sintered alloy 143 of the present invention, the comparative sintered alloys 33 to 34, and the conventional sintered alloy 45 were produced and these cylindrical sintered alloy blocks for piercing test were repeatedly pierced until the drill is damaged, using a high-speed steel drill having a diameter of 1.2 mm, under the following conditions:

-   Rotating speed: 5000 rpm -   Feed speed: 0.006 mm/rev. -   Cutting oil: none (dry).

The number of piercing (maximum number of piercing, lifetime) of one new drill was measured. The results are shown in Table 17-2. Machinability was evaluated by the results. TABLE 17-1 Component ratio of raw powder (mass %) CaCO₃ powder Co- Average particle size based Cr-based Fe-based Iron-based sintered is described in Mo alloy alloy Ni C Co alloy Fe alloy parenthesis. powder powder# powder# powder powder powder powder# Infiltration Cu powder Product of the 143  0.5 (0.6 μm) 1.5 5.0 19.0 3.0 1.5 4.4 9.0 18 balance present invention Comparative 33 0.02* (40 μm*) 1.5 5.0 19.0 3.0 1.5 4.4 9.0 18 balance products 34  3.5* (0.01 μm*) 1.5 5.0 19.0 3.0 1.5 4.4 9.0 18 balance Conventional 45 CaF₂:1 1.5 5.0 19.0 3.0 1.5 4.4 9.0 18 balance product Fe-based alloy powder#: Fe—13%Cr—5%Nb—0.8%Si Co-based alloy powder#: Co—30%Mo—10%Cr—3%Si Cr-based alloy powder#: Cr—25%Co—25%W—115%Fe—1%Nb—1%Si—1.5%C The symbol * means the value which is not within the scope of the present invention.

TABLE 17-2 Component ratio of iron-based sintered alloy (mass %) Number of Iron-based sintered Fe and inevitable piercing alloy CaCO₃ C Cr Mo W Ni Si Co Nb Cu impurities (times) Remarks Product of the present 143 0.47 1.8 8 3 4.8 5 0.4 12 1.1 18 balance 346 — invention Comparative products 33 0.01* 1.8 8 3 4.8 5 0.4 12 1.1 18 balance 38 — 34 3.47* 1.8 8 3 4.8 5 0.4 12 1.1 18 balance 205 decrease in strength Conventional product 45 CaF₂:1 1.8 8 3 4.8 5 0.4 12 1.1 18 balance 50 — The symbol * means the value which is not within the scope of the present invention.

As is apparent from the results shown in Table 17-1 and Table 17-2, the number of piercing of the cylindrical sintered alloy block for piercing test made of the sintered alloy 143 of the present invention is larger than that of the cylindrical sintered alloy block for piercing test made of the conventional sintered alloy 45 and therefore the sintered alloy of the present invention is excellent in machinability. However, the comparative sintered alloy 33 containing CaCO₃ in the content of less than the range defined in the present invention is inferior in machinability because of small number of piercing, while the comparative sintered alloy 34 containing CaCO₃ in the content of more than the range defined in the present invention is excellent in machinability because of large number of piercing, but shows drastically decreased deflection strength, and therefore it is not preferred.

EXAMPLE 18

As raw powders, a CaCO₃ powder having an average particle size of 0.6 μm, a CaF₂ powder having an average particle size of 36 μm, a Fe powder having an average particle size of 80 μm, a Ni powder having an average particle size of 3 μm, a Mo powder having an average particle size of 3 μm, a Co powder having an average particle size of 30 μm and a C powder having an average particle size of 18 μm were prepared. These raw powders were blended according to the formulation shown in Table 18-1, mixed in a double corn mixer and compacted to obtain a green compact, and then the resulting green compact was sintered in a vacuum atmosphere at 0.1 Pa under the conditions of a temperature of 1150° C. and a retention time of 60 minutes to obtain an iron-based sintered alloy 144 of the present invention, comparative sintered alloys 35 to 36, and a conventional sintered alloy 46 shown in Table 18-2.

Cylindrical sintered alloy blocks for piercing test each having a diameter of 30 mm and a height of 10 mm, made of the sintered alloy 144 of the present invention, the comparative sintered alloys 35 to 36, and the conventional sintered alloy 46 were produced and these cylindrical sintered alloy blocks for piercing test were repeatedly pierced until the drill is damaged, using a high-speed steel drill having a diameter of 1.2 mm, under the following conditions:

-   Rotating speed: 5000 rpm -   Feed speed: 0.006 mm/rev. -   Cutting oil: none (dry).

The number of piercing (maximum number of piercing, lifetime) of one new drill was measured. The results are shown in Table 18-2. Machinability was evaluated by the results. TABLE 18-1 Component ratio of raw powder (mass %) CaCO₃ powder Average particle size is Iron-based sintered alloy described in parenthesis. Mo powder Ni powder C powder Co powder Fe powder Product of the present 144  0.5 (0.6 μm) 2.0 2.0 1.3 1.0 balance invention Comparative products 35 0.02* (40 μm*) 2.0 2.0 1.3 1.0 balance 36  3.5* (0.01 μm*) 2.0 2.0 1.3 1.0 balance Conventional product 46 CaF₂:1 2.0 2.0 1.3 1.0 balance The symbol * means the value which is not within the scope of the present invention.

TABLE 18-2 Component ratio of iron-based Number sintered alloy (mass %) of Fe and inevitable piercing Iron-based sintered alloy CaCO₃ C Mo Ni Co impurities (times) Remarks Product 144 0.46 1.3 2 2 1 balance 287 — of the present invention Comparative products 35 0.01* 1.3 2 2 1 balance 27 — 36 3.43* 1.3 2 2 1 balance 167 decrease in strength Conventional product 46 CaF₂:1 1.3 2 2 1 balance 37 — The symbol * means the value which is not within the scope of the present invention.

As is apparent from the results shown in Table 18-1 and Table 18-2, the number of piercing of the cylindrical sintered alloy block for piercing test made of the sintered alloy 144 of the present invention is larger than that of the cylindrical sintered alloy block for piercing test made of the conventional sintered alloy 46 and therefore the sintered alloy of the present invention is excellent in machinability. However, the comparative sintered alloy 35 containing CaCO₃ in the content of less than the range defined in the present invention is inferior in machinability because of small number of piercing, while the comparative sintered alloy 36 containing CaCO₃ in the content of more than the range defined in the present invention is excellent in machinability because of large number of piercing, but shows drastically decreased deflection strength, and therefore it is not preferred.

EXAMPLE 19

As raw powders, a CaCO₃ powder having an average particle size of 0.6 μm, a CaF₂ powder having an average particle size of 36 μm and a SUS316 (Fe-17% Cr-12% Ni-2.5% Mo) powder having an average particle size of 80 μm were prepared. These raw powders were blended according to the formulation shown in Table 19, mixed in a double corn mixer and compacted to obtain a green compact, and then the resulting green compact was sintered in a vacuum atmosphere at 0.1 Pa under the conditions of a temperature of 1200° C. and a retention time of 60 minutes to obtain an iron-based sintered alloy 145 of the present invention, comparative sintered alloys 37 to 38, and a conventional sintered alloy 47.

Cylindrical sintered alloy blocks for piercing test each having a diameter of 30 mm and a height of 10 mm, made of the sintered alloy 145 of the present invention, the comparative sintered alloys 37 to 38, and the conventional sintered alloy 47 were produced and these cylindrical sintered alloy blocks for piercing test were repeatedly pierced until the drill is damaged, using a high-speed steel drill having a diameter of 1.2 mm, under the following conditions:

-   Rotating speed: 5000 rpm -   Feed speed: 0.006 mm/rev. -   Cutting oil: none (dry).

The number of piercing (maximum number of piercing, lifetime) of one new drill was measured. The results are shown in Table 19. Machinability was evaluated by the results. TABLE 19 Component ratio of raw powder (mass %) Component ratio of SUS316 iron-based sintered alloy CaCO₃ powder (Fe—17% (mass %) Average particle size Cr—12% Fe and Number of is described in Ni—2.5% inevitable piercing Iron-based sintered alloy parenthesis. Mo) powder CaCO₃ Cr Ni Mo impurities (times) Remarks Product of the 145 0.5 (0.6 μm) balance 0.48 17.1 12.3 2.2 balance 175 — present invention Comparative 37 0.02* (40 μm*)   balance 0.01* 17.1 12.3 2.2 balance 6 — products 38   35* (0.01 μm*) balance 3.43* 17.1 12.3 2.2 balance 105 decrease in strength Conventional 47 CaF₂:1 balance CaF₂:1 17.1 12.3 2.2 balance 15 — product The symbol * means the value which is not within the scope of the present invention.

As is apparent from the results shown in Table 19, the number of piercing of the cylindrical sintered alloy block for piercing test made of the sintered alloy 145 of the present invention is larger than that of the cylindrical sintered alloy block for piercing test made of the conventional sintered alloy 47 and therefore the sintered alloy of the present invention is excellent in machinability. However, the comparative sintered alloy 37 containing CaCO₃ in the content of less than the range defined in the present invention is inferior in machinability because of small number of piercing, while the comparative sintered alloy 38 containing CaCO₃ in the content of more than the range defined in the present invention is excellent in machinability because of large number of piercing, but shows drastically decreased deflection strength, and therefore it is not preferred.

EXAMPLE 20

As raw powders, a CaCO₃ powder having an average particle size of 0.6 μm, a CaF₂ powder having an average particle size of 36 μm and a SUS430 (Fe-17% Cr) powder having an average particle size of 80 μm were prepared. These raw powders were blended according to the formulation shown in Table 20, mixed in a double corn mixer and compacted to obtain a green compact, and then the resulting green compact was sintered in a vacuum atmosphere at 0.1 Pa under the conditions of a temperature of 1200° C. and a retention time of 60 minutes to obtain an iron-based sintered alloy 146 of the present invention, comparative sintered alloys 39 to 40, and a conventional sintered alloy 48.

Cylindrical sintered alloy blocks for piercing test each having a diameter of 30 mm and a height of 10 mm, made of the sintered alloy 146 of the present invention, the comparative sintered alloys 39 to 40, and the conventional sintered alloy 48 were produced and these cylindrical sintered alloy blocks for piercing test were repeatedly pierced until the drill is damaged, using a high-speed steel drill having a diameter of 1.2 mm, under the following conditions:

-   Rotating speed: 5000 rpm -   Feed speed: 0.006 mm/rev. -   Cutting oil: none (dry).

The number of piercing (maximum number of piercing, lifetime) of one new drill was measured. The results are shown in Table 20. Machinability was evaluated by the results. TABLE 20 Component ratio Component ratio of iron-based of raw powder (mass %) sintered alloy (mass %) CaCO₃ powder SUS430 Fe and Number of Iron-based Average particle size is (Fe—17% inevitable piercing sintered alloy described in parenthesis. Cr) powder CaCO₃ Cr impurities (times) Remarks Product of the present 146 0.5 (0.6 μm) balance 0.45 16.7 balance 193 invention Comparative products 39 0.02 (40 μm*)  balance 0.01* 16.7 balance 24 40   35* (0.01 μm*) balance 3.43* 16.7 balance 134 decrease in strength Conventional product 48 CaF₂:1 balance CaF₂:1 16.7 balance 31 The symbol * means the value which is not within the scope of the present invention.

As is apparent from the results shown in Table 20, the number of piercing of the cylindrical sintered alloy block for piercing test made of the sintered alloy 146 of the present invention is larger than that of the cylindrical sintered alloy block for piercing test made of the conventional sintered alloy 48 and therefore the sintered alloy of the present invention is excellent in machinability. However, the comparative sintered alloy 39 containing CaCO₃ in the content of less than the range defined in the present invention is inferior in machinability because of small number of piercing, while the comparative sintered alloy 40 containing CaCO₃ in the content of more than the range defined in the present invention is excellent in machinability because of large number of piercing, but shows drastically decreased deflection strength, and therefore it is not preferred.

EXAMPLE 21

As raw powders, a CaCO₃ powder having an average particle size of 0.6 μm, a CaF₂ powder having an average particle size of 36 μm, a C powder having an average particle size of 18 μm and a SUS410 (Fe-13% Cr) powder having an average particle size of 80 μm were prepared. These raw powders were blended according to the formulation shown in Table 21, mixed in a double corn mixer and compacted to obtain a green compact, and then the resulting green compact was sintered in a vacuum atmosphere at 0.1 Pa under the conditions of a temperature of 1200° C. and a retention time of 60 minutes to obtain an iron-based sintered alloy 147 of the present invention, comparative sintered alloys 41 to 42, and a conventional sintered alloy 49.

Cylindrical sintered alloy blocks for piercing test each having a diameter of 30 mm and a height of 10 mm, made of the sintered alloy 147 of the present invention, the comparative sintered alloys 41 to 42, and the conventional sintered alloy 49 were produced and these cylindrical sintered alloy blocks for piercing test were repeatedly pierced until the drill is damaged, using a high-speed steel drill having a diameter of 1.2 mm, under the following conditions:

-   Rotating speed: 5000 rpm -   Feed speed: 0.006 mm/rev. -   Cutting oil: none (dry).

The number of piercing (maximum number of piercing, lifetime) of one new drill was measured. The results are shown in Table 21. Machinability was evaluated by the results. TABLE 21 Component ratio of raw powder (mass %) Component ratio of iron-based CaCO₃ powder sintered alloy (mass %) Average particle size is SUS410 Fe and Number of Iron-based described in C (Fe—13% inevitable piercing sintered alloy parenthesis. powder Cr) powder CaCO₃ Cr C impurities (times) Remarks Product of the 147 0.5 (0.6 μm) 0.15 balance 0.49 12.8 0.1 balance 157 — present invention Comparative 41 0.02* (40 μm*)   0.15 balance 0.01* 12.8 0.1 balance 10 — products 42  3.5* (0.01 μm*) 0.15 balance 3.47* 12.8 0.1 balance 115 decrease in strength Conventional 49 CaF₂:1 0.15 balance CaF₂:1 12.8 0.1 balance 18 — product The symbol * means the value which is not within the scope of the present invention.

As is apparent from the results shown in Table 21, the number of piercing of the cylindrical sintered alloy block for piercing test made of the sintered alloy 147 of the present invention is larger than that of the cylindrical sintered alloy block for piercing test made of the conventional sintered alloy 49 and therefore the sintered alloy of the present invention is excellent in machinability. However, the comparative sintered alloy 41 containing CaCO₃ in the content of less than the range defined in the present invention is inferior in machinability because of small number of piercing, while the comparative sintered alloy 42 containing CaCO₃ in the content of more than the range defined in the present invention is excellent in machinability because of large number of piercing, but shows drastically decreased deflection strength, and therefore it is not preferred.

EXAMPLE 22

As raw powders, a CaCO₃ powder having an average particle size of 0.6 μm, a CaF₂ powder having an average particle size of 36 μm and a SUS630 (Fe-17% Cr-4% Ni-4% Cu-0.3% Nb) powder having an average particle size of 80 μm were prepared. These raw powders were blended according to the formulation shown in Table 22, mixed in a double corn mixer and compacted to obtain a green compact, and then the resulting green compact was sintered in a vacuum atmosphere at 0.1 Pa under the conditions of a temperature of 1200° C. and a retention time of 60 minutes to obtain an iron-based sintered alloy 148 of the present invention, comparative sintered alloys 43 to 44, and a conventional sintered alloy 50.

Cylindrical sintered alloy blocks for piercing test each having a diameter of 30 mm and a height of 10 mm, made of the sintered alloy 148 of the present invention, the comparative sintered alloys 43 to 44, and the conventional sintered alloy 50 were produced and these cylindrical sintered alloy blocks for piercing test were repeatedly pierced until the drill is damaged, using a high-speed steel drill having a diameter of 1.2 mm, under the following conditions:

-   Rotating speed: 5000 rpm -   Feed speed: 0.006 mm/rev. -   Cutting oil: none (dry).

The number of piercing (maximum number of piercing, lifetime) of one new drill was measured. The results are shown in Table 22. Machinability was evaluated by the results. TABLE 22 Component ratio of raw powder (mass %) Component ratio of iron-based sintered CaCO₃ powder alloy (mass %) Average particle size Fe and Number of Iron-based is described in #SUS630 inevitable piercing sintered alloy parenthesis. powder CaCO₃ Cr Ni Cu Nb impurities (times) Remarks Product of the present 148 0.5 (0.6 μm) balance 0.45 16.8 4.1 4 0.3 balance 143 — invention Comparative products 43 0.02* (40 μm*)   balance 0.01* 16.8 4.1 4 0.3 balance 13 — 44  3.5* (0.01 μm*) balance 3.43* 16.8 4.1 4 0.3 balance 108 decrease in strength Conventional product 50 CaF₂:1 balance CaF₂:1 16.8 4.1 4 0.3 balance 16 — #SUS630 (Fe—17% Cr—4% Ni—4% Cu—0.3% Nb) The symbol * means the value which is not within the scope of the present invention.

As is apparent from the results shown in Table 22, the number of piercing of the cylindrical sintered alloy block for piercing test made of the sintered alloy 148 of the present invention is larger than that of the cylindrical sintered alloy block for piercing test made of the conventional sintered alloy 50 and therefore the sintered alloy of the present invention is excellent in machinability. However, the comparative sintered alloy 43 containing CaCO₃ in the content of less than the range defined in the present invention is inferior in machinability because of small number of piercing, while the comparative sintered alloy 44 containing CaCO₃ in the content of more than the range defined in the present invention is excellent in machinability because of large number of piercing, but shows drastically decreased deflection strength, and therefore it is not preferred.

EXAMPLE 23

As raw powders, a SrCO₃ powder having an average particle size shown in Table 23 and a pure Fe powder having an average particle size of 80 μm were prepared. These raw powders were blended according to the formulation shown in Table 23, mixed in a double corn mixer and compacted to obtain a green compact, and then the resulting green compact was sintered in an endothermic gas (ratio of components=H₂: 40.5%, CO: 19.8%, CO₂: 0.1%, CH: 0.5%, and N₂: 39.1%) atmosphere under the conditions of a temperature of 1120° C. and a retention time of 20 minutes to obtain iron-based sintered alloys 149 to 158 of the present invention and comparative sintered alloys 45 to 46.

Cylindrical sintered alloy blocks for piercing test each having a diameter of 30 mm and a height of 10 mm, made of the sintered alloys 149 to 158 of the present invention and the comparative sintered alloys 45 to 46 were produced and these cylindrical sintered alloy blocks for piercing test were repeatedly pierced until the drill is damaged, using a high-speed steel drill having a diameter of 1.2 mm, under the following conditions:

-   Rotating speed: 10000 rpm -   Feed speed: 0.030 mm/rev. -   Cutting oil: none (dry).

The number of piercing (maximum number of piercing, lifetime) of one new drill was measured. The results are shown in Table 23. Machinability was evaluated by the results. TABLE 23 Component ratio of Component ratio iron-based sintered of raw powder (mass %) alloy (mass %) SrCO₃ powder Fe and Number of Iron-based Average particle size is inevitable piercing sintered alloy described in parenthesis. Fe powder SrCO₃ impurities (times) Remarks Products of the 149 0.05 (0.1 μm)  balance 0.05 balance 63 — present invention 150 0.2 (0.5 μm) balance 0.19 balance 130 — 151 0.5 (1 μm)   balance 0.49 balance 145 — 152 1.0 (1 μm)   balance 0.98 balance 212 — 153 1.3 (0.5 μm) balance 1.28 balance 190 — 154 1.5 (2 μm)   balance 1.49 balance 245 — 155 1.8 (18 μm)  balance 1.80 balance 197 — 156 2.1 (2 μm)   balance 2.09 balance 188 — 157 2.5 (18 μm)  balance 2.47 balance 219 — 158 3.0 (30 μm)  balance 2.99 balance 305 — Comparative 45 0.02* (40 μm*)   balance 0.01 balance 25 — products 46  3.5* (0.01 μm*) balance 3.47* balance 146 decrease in strength The symbol * means the value which is not within the scope of the present invention.

As is apparent from the results shown in Table 23, the number of piercing of the cylindrical sintered alloy blocks for piercing test made of the sintered alloys 149 to 158 of the present invention is larger than that of the cylindrical sintered alloy blocks for piercing test made of the conventional sintered alloys 1 to 3 shown in Table 1 and therefore the sintered alloys of the present invention are excellent in machinability. However, the comparative sintered alloy 45 containing SrCO₃ in the content of less than the range defined in the present invention is inferior in machinability because of small number of piercing, while the comparative sintered alloy 46 containing SrCO₃ in the content of more than the range defined in the present invention is excellent in machinability because of large number of piercing, but shows drastically decreased deflection strength, and therefore it is not preferred.

EXAMPLE 24

As raw powders, a SrCO₃ powder having an average particle size shown in Table 24 and a Fe-0.6 mass % P powder having an average particle size of 80 μm were prepared. These raw powders were blended according to the formulation shown in Table 24, mixed in a double corn mixer and compacted to obtain a green compact, and then the resulting green compact was sintered in an endothermic gas (ratio of components=H₂: 40.5%, CO: 19.8%, CO₂: 0.1%, CH: 0.5%, and N₂: 39.1%) atmosphere under the conditions of a temperature of 1120° C. and a retention time of 20 minutes to obtain iron-based sintered alloys 159 to 168 of the present invention and comparative sintered alloys 47 to 48.

Cylindrical sintered alloy blocks for piercing test each having a diameter of 30 mm and a height of 10 mm, made of the sintered alloys 159 to 168 of the present invention and the comparative sintered alloys 47 to 48 were produced and these cylindrical sintered alloy blocks for piercing test were repeatedly pierced until the drill is damaged, using a high-speed steel drill having a diameter of 1.2 mm, under the following conditions:

-   Rotating speed: 10000 rpm -   Feed speed: 0.030 mm/rev. -   Cutting oil: none (dry).

The number of piercing (maximum number of piercing, lifetime) of one new drill was measured. The results are shown in Table 24. Machinability was evaluated by the results. TABLE 24 Component ratio of raw powder Component ratio (mass %) of iron-based SrCO₃ powder sintered alloy (mass %) Average particle size is Fe-based Fe and Number of Iron-based described in alloy inevitable piercing sintered alloy parenthesis. powder# SrCO₃ P impurities (times) Remarks Products of the 159 0.05 (0.1 μm)  balance 0.04 0.55 balance 51 — present invention 160 0.2 (0.5 μm) balance 0.18 0.58 balance 121 — 161 0.5 (1 μm)   balance 0.49 0.53 balance 167 — 162 1.0 (1.0 μm) balance 0.99 0.53 balance 169 — 163 1.3 (0.5 μm) balance 1.28 0.57 balance 148 — 184 1.5 (2 μm)   balance 1.48 0.57 balance 178 — 165 1.8 (18 μm)  balance 1.79 0.54 balance 159 — 166 2.1 (2 μm)   balance 2.07 0.53 balance 110 — 167 2.5 (18 μm)  balance 2.49 0.55 balance 135 — 168 3.0 (30 μm)  balance 2.99 0.55 balance 178 — Comparative 47 0.02* (40 μm*)   balance 0.02* 0.56 balance 28 — products 48  3.5* (0.01 μm*) balance 3.48* 0.54 balance 163 decrease in strength The symbol * means the value which is not within the scope of the present invention. #Fe-based alloy powder with the composition of Fe-0.6 mass % P

As is apparent from the results shown in Table 24, the number of piercing of the cylindrical sintered alloy blocks for piercing test made of the sintered alloys 159 to 168 of the present invention is larger than that of the cylindrical sintered alloy blocks for piercing test made of the conventional sintered alloys 4 to 6 shown in Table 2 and therefore the sintered alloys of the present invention are excellent in machinability. However, the comparative sintered alloy 47 containing SrCO₃ in the content of less than the range defined in the present invention is inferior in machinability because of small number of piercing, while the comparative sintered alloy 48 containing SrCO₃ in the content of more than the range defined in the present invention is excellent in machinability because of large number of piercing, but shows drastically decreased deflection strength, and therefore it is not preferred.

EXAMPLE 25

As raw powders, a SrCO₃ powder having an average particle size shown in Table 25, a Fe powder having an average particle size of 80 μm and a C powder having an average particle size of 18 μm were prepared. These raw powders were blended according to the formulation shown in Table 25, mixed in a double corn mixer and compacted to obtain a green compact, and then the resulting green compact was sintered in an endothermic gas (ratio of components=H₂: 40.5%, CO: 19.8%, CO₂: 0.1%, CH: 0.5%, and N₂: 39.1%) atmosphere under the conditions of a temperature of 1120° C. and a retention time of 20 minutes to obtain iron-based sintered alloys 169 to 178 of the present invention and comparative sintered alloys 49 to 50.

Cylindrical sintered alloy blocks for piercing test each having a diameter of 30 mm and a height of 10 mm, made of the sintered alloys 169 to 178 of the present invention and the comparative sintered alloys 49 to 50 were produced and these cylindrical sintered alloy blocks for piercing test were repeatedly pierced until the drill is damaged, using a high-speed steel drill having a diameter of 1.2 mm, under the following conditions:

-   Rotating speed: 10000 rpm -   Feed speed: 0.018 mm/rev. -   Cutting oil: none (dry).

The number of piercing (maximum number of piercing, lifetime) of one new drill was measured. The results are shown in Table 25. Machinability was evaluated by the results. TABLE 25 Component ratio of raw powder (mass %) Component ratio of iron-based SrCO₃ powder sintered alloy (mass %) Iron-based Average particle Fe and Number of sintered size is described C Fe inevitable piercing alloy in parenthesis. powder powder Infiltration Cu SrCO₃ C Cu impurities (times) Remarks Products of 169 0.05 (0.1 μm)  0.13 balance 20 0.05 0.12 19.5 balance 83 — the present 170 0.2 (0.5 μm) 0.3 balance 20 0.20 0.24 20.2 balance 130 — invention 171 0.5 (1 μm)   0.6 balance 20 0.49 0.54 20.1 balance 175 — 172 1.0 (2 μm)   0.8 balance 20 0.97 0.75 19.6 balance 203 — 173 1.3 (0.5 μm) 1.1 balance 20 1.28 1.05 19.9 balance 182 — 174 1.6 (2 μm)   1.1 balance 20 1.46 0.99 20.4 balance 192 — 175 1.8 (18 μm)  1.1 balance 20 1.77 1.05 19.8 balance 183 — 176 2.1 (2 μm)   1.1 balance 20 2.09 1.07 20.0 balance 209 — 177 2.5 (18 μm)  1.1 balance 20 2.45 1.07 19.7 balance 197 — 178 3.0 (30 μm)  1.2 balance 20 2.96 1.15 19.9 balance 172 — Comparative 49 0.02* (40 μm*)   1.1 balance 20 0.01* 1.04 20.3 balance 25 — products 50  3.5* (0.01 μm*) 1.1 balance 20 3.45* 1.06 19.6 balance 124 decrease in strength The symbol * means the value which is not within the scope of the present invention.

As is apparent from the results shown in Table 25, the number of piercing of the cylindrical sintered alloy blocks for piercing test made of the sintered alloys 169 to 178 of the present invention is larger than that of the cylindrical sintered alloy blocks for piercing test made of the conventional sintered alloys 7 to 9 shown in Table 3 and therefore the sintered alloys of the present invention are excellent in machinability. However, the comparative sintered alloy 49 containing SrCO₃ in the content of less than the range defined in the present invention is inferior in machinability because of small number of piercing, while the comparative sintered alloy 50 containing SrCO₃ in the content of more than the range defined in the present invention is excellent in machinability because of large number of piercing, but shows drastically decreased deflection strength, and therefore it is not preferred.

EXAMPLE 26

As raw powders, a SrCO₃ powder having an average particle size shown in Table 26, a Fe powder having an average particle size of 80 μm and a C powder having an average particle size of 18 μm were prepared. These raw powders were blended according to the formulation shown in Table 26, mixed in a double corn mixer and compacted to obtain a green compact, and then the resulting green compact was sintered in an endothermic gas (ratio of components=H2: 40.5%, CO: 19.8%, CO₂: 0.1%, CH: 0.5%, and N₂: 39.1%) atmosphere under the conditions of a temperature of 1120° C. and a retention time of 20 minutes and subjected to 20% Cu infiltration to obtain iron-based sintered alloys 179 to 188 of the present invention and comparative sintered alloys 51 to 52.

Cylindrical sintered alloy blocks for piercing test each having a diameter of 30 mm and a height of 10 mm, made of the sintered alloys 179 to 188 of the present invention and the comparative sintered alloys 51 to 52 were produced and these cylindrical sintered alloy blocks for piercing test were repeatedly pierced until the drill is damaged, using a high-speed steel drill having a diameter of 1.2 mm, under the following conditions:

-   Rotating speed: 10000 rpm -   Feed speed: 0.018 mm/rev. -   Cutting oil: none (dry).

The number of piercing (maximum number of piercing, lifetime) of one new drill was measured. The results are shown in Table 26. Machinability was evaluated by the results. TABLE 26 Component ratio Component ratio of raw powder (mass %) of iron-based sintered SrCO₃ powder alloy (mass %) Iron-based Average particle size Fe and Number of sintered is described in C inevitable piercing alloy parenthesis. powder Fe powder SrCO₃ C impurities (times) Remarks Products of the 179 0.05 (0.1 μm)  0.13 balance 0.05 0.12 balance 75 — present 180 0.2 (0.5 μm) 0.3 balance 0.20 0.24 balance 110 — invention 181 0.5 (1 μm)   0.6 balance 0.49 0.54 balance 156 — 182 1.0 (2 μm)   0.8 balance 0.97 0.75 balance 172 — 183 1.3 (0.5 μm) 1.1 balance 1.28 1.05 balance 181 — 184 1.5 (2 μm)   1.1 balance 1.46 0.99 balance 205 — 185 1.8 (18 μm)  1.1 balance 1.77 1.05 balance 171 — 186 2.1 (2 μm)   1.1 balance 2.09 1.07 balance 220 — 187 2.5 (18 μm)  1.1 balance 2.45 1.07 balance 199 — 188 3.0 (30 μm)  1.2 balance 2.96 1.15 balance 194 — Comparative 51 0.02* (40 μm*)   1.1 balance 0.01* 1.04 balance 15 — products 52  3.5* (0.01 μm*) 1.1 balance 3.45* 1.06 balance 122 decrease in strength The symbol * means the value which is not within the scope of the present invention.

As is apparent from the results shown in Table 26, the number of piercing of the cylindrical sintered alloy blocks for piercing test made of the sintered alloys 179 to 188 of the present invention is larger than that of the cylindrical sintered alloy blocks for piercing test made of the conventional sintered alloys 10 to 12 shown in Table 4 and therefore the sintered alloys of the present invention are excellent in machinability. However, the comparative sintered alloy 51 containing SrCO₃ in the content of less than the range defined in the present invention is inferior in machinability because of small number of piercing, while the comparative sintered alloy 52 containing SrCO₃ in the content of more than the range defined in the present invention is excellent in machinability because of large number of piercing, but shows drastically decreased deflection strength, and therefore it is not preferred.

EXAMPLE 27

As raw powders, a SrCO₃ powder having an average particle size shown in Table 27, a Fe powder having an average particle size of 80 μm, a Cu powder having an average particle size of 25 μm and a C powder having an average particle size of 18 μm were prepared. These raw powders were blended according to the formulation shown in Table 27, mixed in a double corn mixer and compacted to obtain a green compact, and then the resulting green compact was sintered in an endothermic gas (ratio of components=H₂: 40.5%, CO: 19.8%, CO₂: 0.1%, CH: 0.5%, and N₂: 39.1%) atmosphere under the conditions of a temperature of 1120° C. and a retention time of 20 minutes to obtain iron-based sintered alloys 189 to 198 of the present invention and comparative sintered alloys 53 to 54.

Cylindrical sintered alloy blocks for piercing test each having a diameter of 30 mm and a height of 10 mm, made of the sintered alloys 189 to 198 of the present invention and the comparative sintered alloys 53 to 54 were produced and these cylindrical sintered alloy blocks for piercing test were repeatedly pierced until the drill is damaged, using a high-speed steel drill having a diameter of 1.2 mm, under the following conditions:

-   Rotating speed: 10000 rpm -   Feed speed: 0.030 mm/rev. -   Cutting oil: none (dry).

The number of piercing (maximum number of piercing, lifetime) of one new drill was measured. The results are shown in Table 27. Machinability was evaluated by the results. TABLE 27 Component ratio of raw powder (mass %) Component ratio of iron-based SrCO₃ powder sintered alloy (mass %) Iron-based Average particle size Fe and Number of sintered is described in Cu C Fe inevitable piercing alloy parenthesis. powder powder powder SrCO₃ Cu C impurities (times) Remarks Products of the 189 0.05 (0.1 μm)  0.2 0.13 balance 0.03 2.0 0.11 balance 48 — present 190 0.2 (0.5 μm) 2 0.25 balance 0.18 2.1 0.22 balance 127 — invention 191 0.5 (1 μm)   2 0.98 balance 0.48 1.9 0.87 balance 136 — 192 1.0 (2 μm)   2 0.7 balance 0.96 2.0 0.68 balance 225 — 193 1.3 (0.5 μm) 2 0.7 balance 1.25 2.0 0.64 balance 247 — 194 1.5 (2 μm)   4 0.7 balance 1.46 4.0 0.65 balance 229 — 195 1.8 (18 μm)  5.8 0.7 balance 1.77 5.7 0.67 balance 213 — 196 2.1 (2 μm)   4 0.7 balance 2.09 3.9 0.64 balance 200 — 197 2.5 (18 μm)  2 0.98 balance 2.48 2.0 0.92 balance 179 — 198 3.0 (30 μm)  2 1.2 balance 2.97 2.0 1.16 balance 154 — Comparative 53 0.02* (40 μm*)   2 0.7 balance 0.01* 1.9 0.67 balance 8 — products 54  3.5* (0.01 μm*) 2 0.7 balance 3.47* 2.0 0.65 balance 148 decrease in strength The symbol * means the value which is not within the scope of the present invention.

As is apparent from the results shown in Table 27, the number of piercing of the cylindrical sintered alloy blocks for piercing test made of the sintered alloys 189 to 198 of the present invention is larger than that of the cylindrical sintered alloy blocks for piercing test made of the conventional sintered alloys 13 to 15 shown in Table 5 and therefore the sintered alloys of the present invention are excellent in machinability. However, the comparative sintered alloy 53 containing SrCO₃ in the content of less than the range defined in the present invention is inferior in machinability because of small number of piercing, while the comparative sintered alloy 54 containing SrCO₃ in the content of more than the range defined in the present invention is excellent in machinability because of large number of piercing, but shows drastically decreased deflection strength, and therefore it is not preferred.

EXAMPLE 28

As raw powders, a SrCO₃ powder having an average particle size shown in Table 28, a partially diffused Fe-based alloy powder having an average particle size of 80 μm with the composition of Fe-1.5% Cu-4.0% Ni-0.5% Mo and a C powder having an average particle size of 18 μm were prepared. These raw powders were blended according to the formulation shown in Table 28, mixed in a double corn mixer and compacted to obtain a green compact, and then the resulting green compact was sintered in an endothermic gas (ratio of components=H₂: 40.5%, CO: 19.8%, CO₂: 0.1%, CH: 0.5%, and N₂: 39.1%) atmosphere under the conditions of a temperature of 1120° C. and a retention time of 20 minutes to obtain iron-based sintered alloys 199 to 208 of the present invention and comparative sintered alloys 55 to 56.

Cylindrical sintered alloy blocks for piercing test each having a diameter of 30 mm and a height of 10 mm, made of the sintered alloys 199 to 208 of the present invention and the comparative sintered alloys 55 to 56 were produced and these cylindrical sintered alloy blocks for piercing test were repeatedly pierced until the drill is damaged, using a high-speed steel drill having a diameter of 1.2 mm, under the following conditions:

-   Rotating speed: 5000 rpm -   Feed speed: 0.006 mm/rev. -   Cutting oil: none (dry).

The number of piercing (maximum number of piercing, lifetime) of one new drill was measured. The results are shown in Table 28. Machinability was evaluated by the results. TABLE 28 Component ratio of raw powder (mass %) Component ratio of iron-based sintered alloy SrCO₃ powder (mass %) Iron-based Average particle Fe-based Fe and Number of sintered size is described in C alloy inevitable piercing alloy parenthesis. powder powder# SrCO₃ Cu C Ni Mo impurities (times) Remarks Products of the 199  0.05 (0.1 μm) 0.13 balance 0.03 1.5 0.11 3.9 0.50 balance 51 — present 200  0.2 (0.5 μm) 0.25 balance 0.18 1.5 0.19 4.0 0.50 balance 148 — invention 201  0.5 (1 μm) 0.98 balance 0.46 1.5 0.85 4.0 0.50 balance 208 — 202  1.0 (2 μm) 0.5 balance 0.96 1.4 0.47 4.1 0.52 balance 308 — 203  1.3 (0.5 μm) 0.5 balance 1.25 1.5 0.45 4.0 0.50 balance 301 — 204  1.5 (2 μm) 0.5 balance 1.45 1.5 0.45 4.0 0.50 balance 315 — 205  1.8 (18 μm) 0.5 balance 1.72 1.5 0.47 4.0 0.49 balance 268 — 206  2.1 (2 μm) 0.5 balance 2.05 1.6 0.47 3.8 0.50 balance 298 — 207  2.5 (18 μm) 1.0 balance 2.44 1.5 0.90 4.0 0.50 balance 286 — 208  3.0 (30 μm) 1.2 balance 2.93 1.5 1.17 4.0 0.50 balance 248 — Comparative 55 0.02* (40 μm*) 0.5 balance 0.01* 1.5 0.43 4.1 0.50 balance 9 — products 56  3.5* (0.01 μm*) 0.5 balance 3.42* 1.5 0.44 4.0 0.51 balance 130 decrease in strength The symbol * means the value which is not within the scope of the present invention. #partially diffused Fe-based alloy powder having an average particle size of 80 μm with the composition of Fe—1.5% Cu—4.0% Ni—0.5% Mo

As is apparent from the results shown in Table 28, the number of piercing of the cylindrical sintered alloy blocks for piercing test made of the sintered alloys 199 to 208 of the present invention is larger than that of the cylindrical sintered alloy blocks for piercing test made of the conventional sintered alloys 16 to 18 shown in Table 6 and therefore the sintered alloys of the present invention are excellent in machinability. However, the comparative sintered alloy 55 containing SrCO₃ in the content of less than the range defined in the present invention is inferior in machinability because of small number of piercing, while the comparative sintered alloy 56 containing SrCO₃ in the content of more than the range defined in the present invention is excellent in machinability because of large number of piercing, but shows drastically decreased deflection strength, and therefore it is not preferred.

EXAMPLE 29

As raw powders, a SrCO₃ powder having an average particle size shown in Table 29, a Fe-based alloy powder having an average particle size of 80 μm with the composition of Fe-1.5% Mo and a C powder having an average particle size of 18 μm were prepared. These raw powders were blended according to the formulation shown in Table 29, mixed in a double corn mixer and compacted to obtain a green compact, and then the resulting green compact was sintered in an endothermic gas (ratio of components=H₂: 40.5%, CO: 19.8%, CO₂: 0.1%, CH: 0.5%, and N₂: 39.1%) atmosphere under the conditions of a temperature of 1120° C. and a retention time of 20 minutes to obtain iron-based sintered alloys 209 to 218 of the present invention and comparative sintered alloys 57 to 58.

Cylindrical sintered alloy blocks for piercing test each having a diameter of 30 mm and a height of 10 mm, made of the sintered alloys 209 to 218 of the present invention and the comparative sintered alloys 57 to 58 were produced and these cylindrical sintered alloy blocks for piercing test were repeatedly pierced until the drill is damaged, using a high-speed steel drill having a diameter of 1.2 mm, under the following conditions:

-   Rotating speed: 5000 rpm -   Feed speed: 0.006 mm/rev. -   Cutting oil: none (dry).

The number of piercing (maximum number of piercing, lifetime) of one new drill was measured. The results are shown in Table 29. Machinability was evaluated by the results. TABLE 29 Component ratio of raw powder (mass %) Component ratio of iron-based SrCO₃ powder sintered alloy (mass %) Iron-based Average particle size Fe-based Fe and Number of sintered is described in C alloy inevitable piercing alloy parenthesis. powder powder# SrCO₃ C Mo impurities (times) Remarks Products of the 209  0.05 (0.1 μm) 0.13 balance 0.04 0.11 1.48 balance 55 — present 210  0.2 (0.5 μm) 0.25 balance 0.18 0.19 1.48 balance 89 — invention 211  0.5 (1 μm) 0.98 balance 0.48 0.88 1.50 balance 83 — 212  1.0 (2 μm) 0.5 balance 0.98 0.45 1.51 balance 187 — 213  1.3 (0.5 μm) 0.5 balance 1.25 0.44 1.50 balance 214 — 214  1.5 (2 μm) 0.5 balance 1.46 0.47 1.51 balance 235 — 215  1.8 (18 μm) 0.5 balance 1.73 0.43 1.46 balance 210 — 216  2.1 (2 μm) 0.5 balance 2.01 0.48 1.48 balance 222 — 217  2.5 (18 μm) 1.0 balance 2.45 0.96 1.50 balance 156 — 218  3.0 (30 μm) 1.2 balance 2.93 1.13 1.48 balance 169 — Comparative 57 0.02* (40 μm*) 0.5 balance 0.01* 0.45 1.50 balance 18 — products 58  3.5* (0.01 μm*) 0.5 balance 3.47* 0.46 1.50 balance 106 decrease in strength The symbol * means the value which is not within the scope of the present invention. #Fe-based alloy powder having a particle size of 80 μm with the composition of Fe—1.5% Mo

As is apparent from the results shown in Table 29, the number of piercing of the cylindrical sintered alloy blocks for piercing test made of the sintered alloys 209 to 218 of the present invention is larger than that of the cylindrical sintered alloy blocks for piercing test made of the conventional sintered alloys 19 to 21 shown in Table 7 and therefore the sintered alloys of the present invention are excellent in machinability. However, the comparative sintered alloy 57 containing SrCO₃ in the content of less than the range defined in the present invention is inferior in machinability because of small number of piercing, while the comparative sintered alloy 58 containing SrCO₃ in the content of more than the range defined in the present invention is excellent in machinability because of large number of piercing, but shows drastically decreased deflection strength, and therefore it is not preferred.

EXAMPLE 30

As raw powders, a SrCO₃ powder having an average particle size shown in Table 30, a Fe-based alloy powder having an average particle size of 80 μm with the composition of Fe-3.0% Cr-0.5% Mo and a C powder having an average particle size of 18 μm were prepared. These raw powders were blended according to the formulation shown in Table 30, mixed in a double corn mixer and compacted to obtain a green compact, and then the resulting green compact was sintered in an N₂+5% H₂ gas mixture under the conditions of a temperature of 1120° C. and a retention time of 20 minutes to obtain iron-based sintered alloys 219 to 228 of the present invention and comparative sintered alloys 59 to 60.

Cylindrical sintered alloy blocks for piercing test each having a diameter of 30 mm and a height of 10 mm, made of the sintered alloys 219 to 228 of the present invention and the comparative sintered alloys 59 to 60 were produced and these cylindrical sintered alloy blocks for piercing test were repeatedly pierced until the drill is damaged, using a high-speed steel drill having a diameter of 1.2 mm, under the following conditions:

-   Rotating speed: 10000 rpm -   Feed speed: 0.006 mm/rev. -   Cutting oil: none (dry).

The number of piercing (maximum number of piercing, lifetime) of one new drill was measured. The results are shown in Table 30. Machinability was evaluated by the results. TABLE 30 Component ratio of raw powder (mass %) Component ratio of iron-based sintered SrCO₃ powder alloy (mass %) Average particle size Fe-based Fe and Number of Iron-based is described in C alloy inevitable piercing sintered alloy parenthesis. powder powder# SrCO₃ C Cr Mo impurities (times) Remarks Products of the 219  0.05 (0.1 μm) 0.13 balance 0.03 0.11 3.0 0.50 balance 56 — present 220  0.2 (0.5 μm) 0.25 balance 0.19 0.19 3.0 0.50 balance 87 — invention 221  0.5 (1 μm) 0.98 balance 0.48 0.85 3.0 0.51 balance 98 — 222  1.0 (2 μm) 0.5 balance 0.97 0.47 3.0 0.50 balance 150 — 223  1.3 (0.5 μm) 0.5 balance 1.27 0.45 2.9 0.50 balance 203 — 224  1.5 (2 μm) 0.5 balance 1.44 0.45 3.0 0.51 balance 211 — 225  1.8 (18 μm) 0.5 balance 1.72 0.44 3.0 0.49 balance 175 — 226  2.1 (2 μm) 0.5 balance 1.95 0.44 3.1 0.48 balance 188 — 227  2.5 (18 μm) 1.0 balance 2.39 0.90 3.0 0.50 balance 142 — 228  3.0 (30 μm) 1.2 Balance 2.91 1.17 3.0 0.50 balance 111 — Comparative 59 0.02* (40 μm*) 0.5 balance 0.01* 0.43 3.1 0.50 balance 2 — products 60  3.5* (0.01 μm*) 0.5 balance 3.45* 0.45 3.0 0.50 balance 98 decrease in strength The symbol * means the value which is not within the scope of the present invention. #Fe-based alloy powder having a particle size of: 80 μm with the composition of Fe—3.0% Cr—0.5% Mo

As is apparent from the results shown in Table 30, the number of piercing of the cylindrical sintered alloy blocks for piercing test made of the sintered alloys 219 to 228 of the present invention is larger than that of the cylindrical sintered alloy blocks for piercing test made of the conventional sintered alloys 22 to 24 shown in Table 8 and therefore the sintered alloys of the present invention are excellent in machinability. However, the comparative sintered alloy 59 containing SrCO₃ in the content of less than the range defined in the present invention is inferior in machinability because of small number of piercing, while the comparative sintered alloy 60 containing SrCO₃ in the content of more than the range defined in the present invention is excellent in machinability because of large number of piercing, but shows drastically decreased deflection strength, and therefore it is not preferred.

EXAMPLE 31

As raw powders, a SrCO₃ powder having an average particle size shown in Table 31, a Fe-based alloy powder having an average particle size of 80 μm with the composition of Fe-3.0% Cr-0.5% Mo, a Ni powder having an average particle size of 3 μm and a C powder having an average particle size of 18 μm were prepared. These raw powders were blended according to the formulation shown in Table 31, mixed in a double corn mixer and compacted to obtain a green compact, and then the resulting green compact was sintered in an N₂+5% H₂ gas mixture under the conditions of a temperature of 1120° C. and a retention time of 20 minutes to obtain iron-based sintered alloys 229 to 238 of the present invention and comparative sintered alloys 61 to 62.

Cylindrical sintered alloy blocks for piercing test each having a diameter of 30 mm and a height of 10 mm, made of the sintered alloys 229 to 238 of the present invention and the comparative sintered alloys 61 to 62 were produced and these cylindrical sintered alloy blocks for piercing test were repeatedly pierced until the drill is damaged, using a high-speed steel drill having a diameter of 1.2 mm, under the following conditions:

-   Rotating speed: 5000 rpm -   Feed speed: 0.006 mm/rev. -   Cutting oil: none (dry).

The number of piercing (maximum number of piercing, lifetime) of one new drill was measured. The results are shown in Table 31. Machinability was evaluated by the results. TABLE 31 Component ratio of raw powder (mass %) Component ratio of iron-based sintered alloy SrCO₃ powder (mass %) Number Iron-based Average particle Fe-based Fe and of sintered size is described C Ni alloy inevitable piercing alloy in parenthesis. powder powder powder# SrCO₃ C Ni Cr Mo impurities (times) Remarks Products of 229  0.05 (0.1 μm) 0.13 0.2 balance 0.03 0.11 0.2 3.0 0.50 balance 57 — the present 230  0.2 (0.5 μm) 0.25 2 balance 0.19 0.19 1.9 2.8 0.50 balance 100 — invention 231  0.5 (1 μm) 0.98 4 balance 0.48 0.85 4.1 3.0 0.49 balance 125 — 232  1.0 (2 μm) 0.5 4 balance 0.97 0.47 4.0 3.0 0.50 balance 184 — 233  1.3 (0.5 μm) 0.5 4 balance 1.27 0.45 4.0 2.9 0.50 balance 122 — 234  1.5 (2 μm) 0.5 4 balance 1.44 0.45 4.0 3.0 0.49 balance 145 — 235  1.8 (18 μm) 0.5 4 balance 1.72 0.44 3.9 2.9 0.49 balance 144 — 236  2.1 (2 μm) 0.5 6 balance 1.95 0.44 6.0 3.0 0.50 balance 135 — 237  2.5 (18 μm) 1.0 8 balance 2.39 0.90 7.9 3.0 0.50 balance 126 — 238  3.0 (30 μm) 1.2 9.8 balance 2.91 1.17 9.8 3.0 0.50 balance 108 — Comparative 61 0.02* (40 μm*) 0.5 4 balance 0.01* 0.43 4.0 3.0 0.50 balance 5 — products 62  3.5* (0.01 μm*) 0.5 4 balance 3.45* 0.45 4.0 3.0 0.50 balance 120 decrease in strength The symbol * means the value which is not within the scope of the present invention. #Fe-based alloy powder having a particle size of: 80 μm with the composition of Fe—3.0% Cr—0.5% Mo

As is apparent from the results shown in Table 31, the number of piercing of the cylindrical sintered alloy blocks for piercing test made of the sintered alloys 229 to 238 of the present invention is larger than that of the cylindrical sintered alloy blocks for piercing test made of the conventional sintered alloys 25 to 27 shown in Table 9 and therefore the sintered alloys of the present invention are excellent in machinability. However, the comparative sintered alloy 61 containing SrCO₃ in the content of less than the range defined in the present invention is inferior in machinability because of small number of piercing, while the comparative sintered alloy 62 containing SrCO₃ in the content of more than the range defined in the present invention is excellent in machinability because of large number of piercing, but shows drastically decreased deflection strength, and therefore it is not preferred.

EXAMPLE 32

As raw powders, a SrCO₃ powder having an average particle size shown in Table 32, a Fe-based alloy powder having an average particle size of 80 μm with the composition of Fe-3.0% Cr-0.5% Mo, a Cu powder having an average particle size of 25 μm, a Ni powder having an average particle size of 3 μm and a C powder having an average particle size of 18 μm were prepared. These raw powders were blended according to the formulation shown in Table 32, mixed in a double corn mixer and compacted to obtain a green compact, and then the resulting green compact was sintered in an N₂+5% H₂ gas mixture under the conditions of a temperature of 1120° C. and a retention time of 20 minutes to obtain iron-based sintered alloys 239 to 248 of the present invention and comparative sintered alloys 63 to 64.

Cylindrical sintered alloy blocks for piercing test each having a diameter of 30 mm and a height of 10 mm, made of the sintered alloys 239 to 248 of the present invention and the comparative sintered alloys 63 to 64 were produced and these cylindrical sintered alloy blocks for piercing test were repeatedly pierced until the drill is damaged, using a high-speed steel drill having a diameter of 1.2 mm, under the following conditions:

-   Rotating speed: 5000 rpm -   Feed speed: 0.006 mm/rev. -   Cutting oil: none (dry).

The number of piercing (maximum number of piercing, lifetime) of one new drill was measured. The results are shown in Table 32. Machinability was evaluated by the results. TABLE 32 Component ratio of raw powder (mass %) SrCO₃ powder Component ratio of iron-based Average sintered alloy (mass %) Number Iron-based particle size is Fe-based Fe and of sintered described in Cu C Ni alloy inevitable piercing alloy parenthesis. powder powder powder powder# SrCO₃ Cu C Ni Cr Mo impurities (times) Remarks Products of 239  0.05 (0.1 μm) 0.2 0.13 0.2 balance 0.03 0.2 0.11 0.2 3.0 0.50 balance 31 — the present 240  0.2 (0.5 μm) 2 0.25 2 balance 0.19 2.1 0.22 2.0 3.0 0.50 balance 95 — invention 241  0.5 (1 μm) 2 0.98 4 balance 0.48 1.9 0.92 4.0 3.0 0.49 balance 108 — 242  1.0 (2 μm) 2 0.5 4 balance 0.97 2.0 0.47 4.0 3.1 0.51 balance 145 — 243  1.3 (0.5 μm) 2 0.5 4 balance 1.27 2.0 0.47 3.9 2.9 0.50 balance 149 — 244  1.5 (2 μm) 4 0.5 4 balance 1.44 4.0 0.45 4.0 3.0 0.50 balance 143 — 245  1.8 (18 μm) 5.8 0.5 4 balance 1.77 5.8 0.45 4.0 3.0 0.49 balance 136 — 246  2.1 (2 μm) 4 0.5 6 balance 2.04 4.0 0.44 6.0 3.0 0.50 balance 151 — 247  2.5 (18 μm) 2 1.0 8 balance 2.42 2.0 0.94 7.9 3.0 0.50 balance 140 — 248  3.0 (30 μm) 2 1.2 9.8 balance 2.96 2.0 1.15 9.8 3.0 0.50 balance 121 — Comparative 63 0.02* (40 μm*) 2 0.5 4 balance 0.01* 1.9 0.46 4.1 3.0 0.50 balance 3 — products 64  3.5* 2 0.5 4 balance 3.46* 2.0 0.45 4.0 3.0 0.50 balance 125 decrease (0.01 μm*) in strength The symbol * means the value which is not within the scope of the present invention. #Fe-based alloy powder having a particle size of 80 μm with the composition of Fe—3.0% Cr—0.5% Mo

As is apparent from the results shown in Table 32, the number of piercing of the cylindrical sintered alloy blocks for piercing test made of the sintered alloys 239 to 248 of the present invention is larger than that of the cylindrical sintered alloy blocks for piercing test made of the conventional sintered alloys 28 to 30 shown in Table 10 and therefore the sintered alloys of the present invention are excellent in machinability. However, the comparative sintered alloy 63 containing SrCO₃ in the content of less than the range defined in the present invention is inferior in machinability because of small number of piercing, while the comparative sintered alloy 64 containing SrCO₃ in the content of more than the range defined in the present invention is excellent in machinability because of large number of piercing, but shows drastically decreased deflection strength, and therefore it is not preferred.

EXAMPLE 33

As raw powders, a SrCO₃ powder having an average particle size shown in Table 33, a Fe powder having an average particle size of 80 μm, a Ni powder having an average particle size of 3 μm and a C powder having an average particle size of 18 μm were prepared. These raw powders were blended according to the formulation shown in Table 33, mixed in a double corn mixer and compacted to obtain a green compact, and then the resulting green compact was sintered in an endothermic gas (ratio of components=H₂: 40.5%, CO: 19.8%, CO₂: 0.1%, CH: 0.5%, and N₂: 39.1%) atmosphere under the conditions of a temperature of 1120° C. and a retention time of 20 minutes to obtain iron-based sintered alloys 249 to 258 of the present invention and comparative sintered alloys 65 to 66.

Cylindrical sintered alloy blocks for piercing test each having a diameter of 30 mm and a height of 10 mm, made of the sintered alloys 249 to 258 of the present invention and the comparative sintered alloys 65 to 66 were produced and these cylindrical sintered alloy blocks for piercing test were repeatedly pierced until the drill is damaged, using a high-speed steel drill having a diameter of 1.2 mm, under the following conditions:

-   Rotating speed: 5000 rpm -   Feed speed: 0.009 mm/rev. -   Cutting oil: none (dry).

The number of piercing (maximum number of piercing, lifetime) of one new drill was measured. The results are shown in Table 33. Machinability was evaluated by the results. TABLE 33 Component ratio of raw powder (mass %) Component ratio of iron-based SrCO₃ powder sintered alloy (mass %) Iron-based Average particle size Fe and Number of sintered is described in C Ni Fe inevitable piercing alloy parenthesis. powder powder powder SrCO₃ C Ni impurities (times) Remarks Products of the 249  0.05 (0.1 μm) 0.13 0.2 balance 0.04 0.12 0.2 balance 45 — present 250  0.2 (0.5 μm) 0.25 1 balance 0.24 0.23 1.0 balance 80 — invention 251  0.5 (1 μm) 0.98 3 balance 0.47 0.92 2.9 balance 86 — 252  1.0 (2 μm) 0.5 3 balance 0.98 0.46 3.0 balance 202 — 253  1.3 (0.5 μm) 0.5 3 balance 1.28 0.44 3.0 balance 136 — 254  1.5 (2 μm) 0.5 3 balance 1.47 0.47 3.0 balance 187 — 255  1.8 (18 μm) 0.5 3 balance 1.75 0.46 3.0 balance 196 — 256  2.1 (2 μm) 0.5 6 balance 2.06 0.45 6.0 balance 154 — 257  2.5 (18 μm) 1.0 8 balance 2.44 0.92 8.0 balance 136 — 258  3.0 (30 μm) 1.2 9.8 balance 2.98 1.13 9.8 balance 95 — Comparative 65 0.02* (40 μm*) 0.5 3 balance 0.01* 0.45 3.0 balance 5 — products 66  3.5* (0.01 μm*) 0.5 3 balance 3.49* 0.45 3.0 balance 137 decrease in strength The symbol * means the value which is not within the scope of the present invention.

As is apparent from the results shown in Table 33, the number of piercing of the cylindrical sintered alloy blocks for piercing test made of the sintered alloys 249 to 258 of the present invention is larger than that of the cylindrical sintered alloy blocks for piercing test made of the conventional sintered alloys 31 to 33 shown in Table 11 and therefore the sintered alloys of the present invention are excellent in machinability. However, the comparative sintered alloy 65 containing SrCO₃ in the content of less than the range defined in the present invention is inferior in machinability because of small number of piercing, while the comparative sintered alloy 66 containing SrCO₃ in the content of more than the range defined in the present invention is excellent in machinability because of large number of piercing, but shows drastically decreased deflection strength, and therefore it is not preferred.

EXAMPLE 34

As raw powders, a SrCO₃ powder having an average particle size shown in Table 34, a Fe powder having an average particle size of 80 μm, a Ni powder having an average particle size of 3 μm, a Mo powder having an average particle size of 3 μm and a C powder having an average particle size of 18 μm were prepared. These raw powders were blended according to the formulation shown in Table 34, mixed in a double corn mixer and compacted to obtain a green compact, and then the resulting green compact was sintered in an endothermic gas (ratio of components=H₂: 40.5%, CO: 19.8%, CO₂: 0.1%, CH: 0.5%, and N₂: 39.1%) atmosphere under the conditions of a temperature of 1120° C. and a retention time of 20 minutes to obtain iron-based sintered alloys 259 to 268 of the present invention and comparative sintered alloys 67 to 68. Cylindrical sintered alloy blocks for piercing test each having a diameter of 30 mm and a height of 10 mm, made of the sintered alloys 259 to 268 of the present invention and the comparative sintered alloys 67 to 68 were produced and these cylindrical sintered alloy blocks for piercing test were repeatedly pierced until the drill is damaged, using a high-speed steel drill having a diameter of 1.2 mm, under the following conditions:

-   Rotating speed: 5000 rpm -   Feed speed: 0.009 mm/rev. -   Cutting oil: none (dry).

The number of piercing (maximum number of piercing, lifetime) of one new drill was measured. The results are shown in Table 34. Machinability was evaluated by the results. TABLE 34 Component ratio of raw powder (mass %) Component ratio of iron-based SrCO₃ powder sintered alloy (mass %) Number Iron-based Average particle Fe and of sintered size is described C Ni Mo Fe inevitable piercing alloy in parenthesis. powder powder powder powder SrCO₃ C Ni Mo impurities (times) Remarks Products of 259 0.05 (0.1 μm) 0.13 0.2 0.2 balance 0.05 0.11 0.2 0.2 balance 55 — the present 260  0.2 (0.5 μm) 0.25 1 0.3 balance 0.19 0.18 1.0 0.3 balance 101 — invention 261  0.5 (1 μm) 0.98 4 0.5 balance 0.44 0.93 4.0 0.5 balance 103 — 262  1.0 (2 μm) 0.6 4 0.5 balance 0.98 0.55 4.0 0.5 balance 204 — 263  1.3 (0.5 μm) 0.6 4 0.5 balance 1.28 0.57 4.0 0.5 balance 214 — 264  1.5 (2 μm) 0.6 4 1 balance 1.48 0.54 3.9 1.0 balance 187 — 265  1.8 (18 μm) 0.6 4 3 balance 0.76 0.54 3.9 2.9 balance 169 — 266  2.1 (2 μm) 0.6 6 4.8 balance 1.94 0.54 6.0 4.7 balance 159 — 267  2.5 (18 μm) 1.0 8 0.5 balance 2.47 0.95 8.0 0.5 balance 128 — 268  3.0 (30 μm) 1.2 9.8 0.5 balance 2.95 1.14 9.8 0.5 balance 159 — Comparative 67 0.02* 0.6 4 0.5 balance 0.01* 0.54 4.0 0.5 balance 9 — products (40 μm*) 68 3.5* 0.6 4 0.5 balance 3.46* 0.54 4.0 0.5 balance 106 decrease (6.01 μm*) in strength The symbol * means the value which is not within the scope of the present invention.

As is apparent from the results shown in Table 34, the number of piercing of the cylindrical sintered alloy blocks for piercing test made of the sintered alloys 259 to 268 of the present invention is larger than that of the cylindrical sintered alloy blocks for piercing test made of the conventional sintered alloys 34 to 36 shown in Table 12 and therefore the sintered alloys of the present invention are excellent in machinability. However, the comparative sintered alloy 67 containing SrCO₃ in the content of less than the range defined in the present invention is inferior in machinability because of small number of piercing, while the comparative sintered alloy 68 containing SrCO₃ in the content of more than the range defined in the present invention is excellent in machinability because of large number of piercing, but shows drastically decreased deflection strength, and therefore it is not preferred.

EXAMPLE 35

As raw powders, a SrCO₃ powder having an average particle size shown in Table 35, a Fe powder having an average particle size of 80 μm, a Ni powder having an average particle size of 3 μm, a Cu powder having an average particle size of 25 μm and a C powder having an average particle size of 18 μm were prepared. These raw powders were blended according to the formulation shown in Table 35, mixed in a double corn mixer and compacted to obtain a green compact, and then the resulting green compact was sintered in an endothermic gas (ratio of components H₂: 40.5%, CO: 19.8%, CO₂: 0.1%, CH: 0.5%, and N₂: 39.1%) atmosphere under the conditions of a temperature of 1120° C. and a retention time of 20 minutes to obtain iron-based sintered alloys 269 to 278 of the present invention and comparative sintered alloys 69 to 70.

Cylindrical sintered alloy blocks for piercing test each having a diameter of 30 mm and a height of 10 mm, made of the sintered alloys 269 to 278 of the present invention and the comparative sintered alloys 69 to 70 were produced and these cylindrical sintered alloy blocks for piercing test were repeatedly pierced until the drill is damaged, using a high-speed steel drill having a diameter of 1.2 mm, under the following conditions:

-   Rotating speed: 5000 rpm -   Feed speed: 0.009 mm/rev. -   Cutting oil: none (dry).

The number of piercing (maximum number of piercing, lifetime) of one new drill was measured. The results are shown in Table 35. Machinability was evaluated by the results. TABLE 35 Component ratio of raw powder (mass %) Component ratio of iron-based sintered SrCO₃ powder alloy (mass %) Iron-based Average particle size Fe and Number of sintered is described in Cu C Ni Fe inevitable piercing alloy parenthesis. powder powder powder powder SrCO₃ Cu C Ni impurities (times) Remarks Products of 269 0.05 (0.1 μm) 0.2 0.13 0.2 balance 0.04 0.2 0.11 0.2 balance 49 — the present 270  0.2 (0.5 μm) 1 0.25 1 balance 0.19 1.0 0.21 1.0 balance 100 — invention 271  0.5 (1 μm) 1 0.98 3 balance 0.45 1.0 0.95 3.0 balance 128 — 272  1.0 (2 μm) 1 0.6 3 balance 0.96 0.99 0.55 3.0 balance 180 — 273  1.3 (0.5 μm) 2 0.6 3 balance 1.27 1.0 0.54 3.0 balance 184 — 274  1.5 (2 μm) 4 0.6 3 balance 1.48 4.0 0.55 2.9 balance 158 — 275  1.8 (18 μm) 5.8 0.6 3 balance 1.76 5.7 0.56 3.0 balance 179 — 276  2.1 (2 μm) 1 0.6 6 balance 1.95 1.0 0.55 6.0 balance 164 — 277  2.5 (18 μm) 1 1.0 8 balance 2.45 1.0 0.91 8.0 balance 155 — 278  3.0 (30 μm) 1 1.2 9.8 balance 2.96 1.0 1.16 9.8 balance 147 — Comparative 69 0.02* 1 0.6 3 balance 0.01* 1.0 0.55 3.0 balance 10 — products (40 μm*) 70 3.5* 1 0.6 3 balance 3.44* 1.0 0.55 3.0 balance 75 decrease in (0.01 μm*) strength The symbol * means the value which is not within the scope of the present invention.

As is apparent from the results shown in Table 35, the number of piercing of the cylindrical sintered alloy blocks for piercing test made of the sintered alloys 269 to 278 of the present invention is larger than that of the cylindrical sintered alloy blocks for piercing test made of the conventional sintered alloys 37 to 39 shown in Table 13 and therefore the sintered alloys of the present invention are excellent in machinability. However, the comparative sintered alloy 69 containing SrCO₃ in the content of less than the range defined in the present invention is inferior in machinability because of small number of piercing, while the comparative sintered alloy 70 containing SrCO₃ in the content of more than the range defined in the present invention is excellent in machinability because of large number of piercing, but shows drastically decreased deflection strength, and therefore it is not preferred

EXAMPLE 36

As raw powders, a SrCO₃ powder having an average particle size shown in Table 36, a Fe powder having an average particle size of 80 μm, a Cu—P powder having an average particle size of 25 μm and a C powder having an average particle size of 18 μm were prepared. These raw powders were blended according to the formulation shown in Table 36, mixed in a double corn mixer and compacted to obtain a green compact, and then the resulting green compact was sintered in an endothermic gas (ratio of components=H₂: 40.5%, CO: 19.8%, CO₂: 0.1%, CH: 0.5%, and N₂: 39.1%) atmosphere under the conditions of a temperature of 1120° C. and a retention time of 20 minutes to obtain iron-based sintered alloys 279 to 288 of the present invention and comparative sintered alloys 71 to 72.

Cylindrical sintered alloy blocks for piercing test each having a diameter of 30 mm and a height of 10 mm, made of the sintered alloys 279 to 288 of the present invention and the comparative sintered alloys 71 to 72 were produced and these cylindrical sintered alloy blocks for piercing test were repeatedly pierced until the drill is damaged, using a high-speed steel drill having a diameter of 1.2 mm, under the following conditions:

-   Rotating speed: 10000 rpm -   Feed speed: 0.009 mm/rev. -   Cutting oil: none (dry).

The number of piercing (maximum number of piercing, lifetime) of one new drill was measured. The results are shown in Table 36. Machinability was evaluated by the results. TABLE 36 Component ratio of raw powder (mass %) Component ratio of iron-based SrCO₃ powder sintered alloy (mass %) Number Iron-based Average particle size Fe and of sintered is described in C Cu—P Fe inevitable piercing alloy parenthesis. powder powder powder SrCO₃ C Cu P impurities (times) Remarks Products of the 279  0.05 (0.1 μm) 1.0 0.7 balance 0.03 0.90 0.6 0.1 balance 71 — present 280  0.2 (0.5 μm) 1.5 1.2 balance 0.17 1.42 1.1 0.1 balance 88 — invention 281  0.5 (1 μm) 1.5 1.8 balance 0.46 1.45 1.6 0.2 balance 102 — 282  1.0 (2 μm) 2.0 1.8 balance 0.95 1.95 1.6 0.2 balance 199 — 283  1.3 (0.5 μm) 2.0 2.8 balance 1.25 1.94 2.5 0.3 balance 240 — 284  1.5 (2 μm) 2.0 2.8 balance 1.44 1.93 2.5 0.3 balance 209 — 285  1.8 (18 μm) 2.0 3.3 balance 1.73 1.94 3 0.3 balance 255 — 286  2.1 (2 μm) 2.5 6.0 balance 1.89 2.45 5.4 0.6 balance 190 — 287  2.5 (18 μm) 2.5 8.0 balance 2.40 2.44 5 0.6 balance 202 — 288  3.0 (30 μm) 3.0 9.0 balance 2.92 2.97 8.2 0.8 balance 265 — Comparative 71 0.02* (40 μm*) 1 2.8 balance 0.01* 0.44 2.5 0.3 balance 5 — products 72  3.5* (0.01 μm*) 1 2.8 balance 3.43* 0.45 2.5 0.3 balance 169 decrease in strength The symbol * means the value which is not within the scope of the present invention.

As is apparent from the results shown in Table 36, the number of piercing of the cylindrical sintered alloy blocks for piercing test made of the sintered alloys 279 to 288 of the present invention is larger than that of the cylindrical sintered alloy blocks for piercing test made of the conventional sintered alloys 40 to 42 shown in Table 14 and therefore the sintered alloys of the present invention are excellent in machinability. However, the comparative sintered alloy 71 containing SrCO₃ in the content of less than the range defined in the present invention is inferior in machinability because of small number of piercing, while the comparative sintered alloy 72 containing SrCO₃ in the content of more than the range defined in the present invention is excellent in machinability because of large number of piercing, but shows drastically decreased deflection strength, and therefore it is not preferred.

EXAMPLE 37

As raw powders, a SrCO₃ powder having an average particle size of 1 m and a Fe-6% Cr-6% Mo-9% W-3% V-10% Co-1.5% C powder having an average particle size of 80 μm were prepared. These raw powders were blended according to the formulation shown in Table 37, mixed in a double corn mixer and compacted to obtain a green compact, and then the resulting green compact was sintered in a dissociated ammonia gas atmosphere under the conditions of a temperature of 1150° C. and a retention time of 60 minutes to obtain an iron-based sintered alloy 289 of the present invention and comparative sintered alloys 73 to 74.

Cylindrical sintered alloy blocks for piercing test each having a diameter of 30 mm and a height of 10 mm, made of the sintered alloy 289 of the present invention and the comparative sintered alloys 73 to 74 were produced and these cylindrical sintered alloy blocks for piercing test were repeatedly pierced until the drill is damaged, using a high-speed steel drill having a diameter of 1.2 mm, under the following conditions:

-   Rotating speed: 5000 rpm -   Feed speed: 0.006 mm/rev. -   Cutting oil: none (dry).

The number of piercing (maximum number of piercing, lifetime) of one new drill was measured. The results are shown in Table 37. Machinability was evaluated by the results. TABLE 37 Component ratio of raw powder (mass %) Fe—6% Cr— SrCO₃ powder 6% Mo— Component ratio of iron-based sintered alloy Average 9% W—3% V— (mass %) Iron-based particle size 10% Co— Fe and Number of sintered is described in 1.5% C inevitable piercing alloy parenthesis. powder SrCO₃ C Cr Mo W Co V impurities (times) Remarks Product of the 289  0.5 (1 μm) balance 0.49 1.5 6 6 9 10 3 balance 150 — present invention Comparative 73 0.02* (40 μm*) balance 0.01* 1.5 6 6 9 10 3 balance 16 — products 74  3.5* (0.01 μm*) balance 3.43* 1.5 6 6 9 10 3 balance 121 decrease in strength The symbol * means the value which is not within the scope of the present invention.

As is apparent from the results shown in Table 37, the number of piercing of the cylindrical sintered alloy block for piercing test made of the sintered alloy 289 of the present invention is larger than that of the cylindrical sintered alloy block for piercing test made of the conventional sintered alloy 43 shown in Table 15 and therefore the sintered alloy of the present invention is excellent in machinability. However, the comparative sintered alloy 73 containing SrCO₃ in the content of less than the range defined in the present invention is inferior in machinability because of small number of piercing, while the comparative sintered alloy 74 containing SrCO₃ in the content of more than the range defined in the present invention is excellent in machinability because of large number of piercing, but shows drastically decreased deflection strength, and therefore it is not preferred.

EXAMPLE 38

As raw powders, a SrCO₃ powder having an average particle size of 1 μm, a Fe-based alloy powder having an average particle size of 80 μm with the composition of Fe-13% Cr-5% Nb-0.8% Si, a Fe powder having an average particle size of 80 μm, a Ni powder having an average particle size of 3 μm, a Mo powder having an average particle size of 3 μm, a Co-based alloy powder having an average particle size of 80 μm with the composition of Co-30% Mo-10% Cr-3% Si, a Cr-based alloy powder having an average particle size of 80 μm with the composition of Cr-25% Co-25% W-11.5% Fe-1% Nb-1% Si-1.5% C, a Co powder having an average particle size of 30 μm and a C powder having an average particle size of 18 μm were prepared. These raw powders were blended according to the formulation shown in Table 38-1, mixed in a double corn mixer and compacted to obtain a green compact, and then the resulting green compact was sintered in a vacuum atmosphere at 0.1 Pa under the conditions of a temperature of 1150° C. and a retention time of 60 minutes to obtain an iron-based sintered alloy 290 of the present invention and comparative sintered alloys 75 to 76 shown in Table 38-2.

Cylindrical sintered alloy blocks for piercing test each having a diameter of 30 mm and a height of 10 mm, made of the sintered alloy 290 of the present invention and the comparative sintered alloys 75 to 76 were produced and these cylindrical sintered alloy blocks for piercing test were repeatedly pierced until the drill is damaged, using a high-speed steel drill having a diameter of 1.2 mm, under the following conditions:

-   Rotating speed: 5000 rpm -   Feed speed: 0.006 mm/rev. -   Cutting oil: none (dry).

The number of piercing (maximum number of piercing, lifetime) of one new drill was measured. The results are shown in Table 38-2. Machinability was evaluated by the results. TABLE 38-1 Component ratio of raw powder (mass %) SrCO₃ powder Average particle size Co-based Cr-based Fe-based is described in Mo alloy alloy Ni C Co alloy Fe Iron-based sintered alloy parenthesis. powder powder# powder# powder powder powder powder# powder Product of the 290  0.5 (1 μm) 9.0 10 12 3 0.8 3.3 10 balance present invention Comparative 75 0.02* (40 μm*) 9.0 10 12 3 0.8 3.3 10 balance products 76  3.5* (0.01 μm*) 9.0 10 12 3 0.8 3.3 10 balance Fe-based alloy powder#: Fe—13% Cr—5% Nb—0.8% Si Co-based alloy powder#: Co—30% Mo—10% Cr—3% S Cr-based alloy powder#: Cr—25% Co—25% W—11.5% Fe—1% Nb—1% Si—1.5% C The symbol * means the value which is not within the scope of the present invention.

TABLE 38-2 Component ratio of iron-based sintered alloy (mass %) Number of Fe and inevitable piercing Iron-based sintered alloy SrCO₃ C Cr Mo W Ni Si Co Nb impurities (times) Remarks Product of the 290 0.47 1 6 12 3 3 0.5 11.7 1.1 balance 265 — present invention Comparative 75 0.01* 1 6 12 3 3 0.5 11.7 1.1 balance 18 — products 76 3.47* 1 6 12 3 3 0.5 11.7 1.1 balance 152 decrease in strength The symbol * means the value which is not within the scope of the present invention.

As is apparent from the results shown in Table 38-1 and Table 38-2, the number of piercing of the cylindrical sintered alloy block for piercing test made of the sintered alloy 290 of the present invention is larger than that of the cylindrical sintered alloy block for piercing test made of the conventional sintered alloy 44 shown in Table 16-1 to Table 16-2 and therefore the sintered alloy of the present invention is excellent in machinability. However, the comparative sintered alloy 75 containing SrCO₃ in the content of less than the range defined in the present invention is inferior in machinability because of small number of piercing, while the comparative sintered alloy 76 containing SrCO₃ in the content of more than the range defined in the present invention is excellent in machinability because of large number of piercing, but shows drastically decreased deflection strength, and therefore it is not preferred.

EXAMPLE 39

As raw powders, a SrCO₃ powder having an average particle size of 1 μm, a Fe-based alloy powder having an average particle size of 80 μm with the composition of Fe-13% Cr-5% Nb-0.8% Si, a Fe powder having an average particle size of 80 μm, a Ni powder having an average particle size of 3 μm, a Mo powder having an average particle size of 3 μm, a Co-based alloy powder having an average particle size of 80 μm with the composition of Co-30% Mo-10% Cr-3% Si, a Cr-based alloy powder having an average particle size of 80 μm with the composition of Cr-25% Co-25% W-11.5% Fe-1% Nb-1% Si-1.5% C, a Co powder having an average particle size of 30 μm and a C powder having an average particle size of 18 μm were prepared. These raw powders were blended according to the formulation shown in Table 39-1, mixed in a double corn mixer and compacted to obtain a green compact, and then the resulting green compact was sintered in a vacuum atmosphere at 0.1 Pa under the conditions of a temperature of 1150° C. and a retention time of 60 minutes and subjected to 18% Cu infiltration to obtain an iron-based sintered alloy 291 of the present invention and comparative sintered alloys 77 to 78 shown in Table 39-2.

Cylindrical sintered alloy blocks for piercing test each having a diameter of 30 mm and a height of 10 mm, made of the sintered alloy 291 of the present invention and the comparative sintered alloys 77 to 78 were produced and these cylindrical sintered alloy blocks for piercing test were repeatedly pierced until the drill is damaged, using a high-speed steel drill having a diameter of 1.2 mm, under the following conditions:

-   Rotating speed: 5000 rpm -   Feed speed: 0.006 mm/rev. -   Cutting oil: none (dry).

The number of piercing (maximum number of piercing, lifetime) of one new drill was measured. The results are shown in Table 39-2. Machinability was evaluated by the results. TABLE 39-1 Component ratio of raw powder (mass %) SrCO₃ powder Average particle Co-based Cr-based Fe-based Iron-based size is described Mo alloy alloy Ni C Co alloy Infiltration Fe sintered alloy in parenthesis. powder powder# powder# powder powder powder powder# Cu powder Product of the 291  0.5 (1 μm) 1.5 5.0 19.0 3.0 1.5 4.4 9.0 18 balance present invention Comparative 77 0.02* (40 μm*) 1.5 5.0 19.0 3.0 1.5 4.4 9.0 18 balance products 78  3.5* (0.01 μm*) 1.5 5.0 19.0 3.0 1.5 4.4 9.0 18 balance Fe-based alloy powder#: Fe—13% Cr—5% Nb—0.8% Si Co-based alloy powder#: Co—30% Mo—10% Cr—3% Si Cr-based alloy powder#: Cr—25% Co—25% W—11.5% Fe—1% Nb—1% Si—1.5% C The symbol * means the value which is not within the scope of the present invention.

TABLE 39-2 Component ratio of iron-based sintered alloy (mass %) Fe and Number of Iron-based inevitable piercing sintered alloy SrCO₃ C Cr Mo W Ni Si Co Nb Cu impurities (times) Remarks Product of the present 291 0.49 1.8 8 3 4.8 5 0.4 12 1.1 18 balance 337 — invention Comparative products 77 0.01* 1.8 8 3 4.8 5 0.4 12 1.1 18 balance 31 — 78 3.47* 1.8 8 3 4.8 5 0.4 12 1.1 18 balance 199 decrease in strength The symbol * means the value which is not within the scope of the present invention.

As is apparent from the results shown in Table 39-1 and Table 39-2, the number of piercing of the cylindrical sintered alloy block for piercing test made of the sintered alloy 291 of the present invention is larger than that of the cylindrical sintered alloy block for piercing test made of the conventional sintered alloy 45 shown in Table 17-1 to Table 17-2 and therefore the sintered alloy of the present invention is excellent in machinability. However, the comparative sintered alloy 77 containing SrCO₃ in the content of less than the range defined in the present invention is inferior in machinability because of small number of piercing, while the comparative sintered alloy 78 containing SrCO₃ in the content of more than the range defined in the present invention is excellent in machinability because of large number of piercing, but shows drastically decreased deflection strength, and therefore it is not preferred.

EXAMPLE 40

As raw powders, a SrCO₃ powder having an average particle size of 1 μm, a Fe powder having an average particle size of 80 μm, a Ni powder having an average particle size of 3 μm, a Mo powder having an average particle size of 3 μm, a Co powder having an average particle size of 30 μm and a C powder having an average particle size of 18 μm were prepared. These raw powders were blended according to the formulation shown in Table 40-1, mixed in a double corn mixer and compacted to obtain a green compact, and then the resulting green compact was sintered in a vacuum atmosphere at 0.1 Pa under the conditions of a temperature of 1150° C. and a retention time of 60 minutes to obtain an iron-based sintered alloy 292 of the present invention and comparative sintered alloys 79 to 80 shown in Table 40-2.

Cylindrical sintered alloy blocks for piercing test each having a diameter of 30 mm and a height of 10 mm, made of the sintered alloy 292 of the present invention and the comparative sintered alloys 79 to 80 were produced and these cylindrical sintered alloy blocks for piercing test were repeatedly pierced until the drill is damaged, using a high-speed steel drill having a diameter of 1.2 mm, under the following conditions:

-   Rotating speed: 5000 rpm -   Feed speed: 0.006 mm/rev. -   Cutting oil: none (dry).

The number of piercing (maximum number of piercing, lifetime) of one new drill was measured. The results are shown in Table 40-2. Machinability was evaluated by the results. TABLE 40-1 Component ratio of raw powder (mass %) SrCO₃ powder Average particle size is described in Mo Iron-based sintered alloy parenthesis. powder Ni powder C powder Co powder Fe powder Product of the present invention 292  0.5 (1 μm) 2.0 2.0 1.3 1.0 balance Comparative products 79 0.02* (40 μm*) 2.0 2.0 1.3 1.0 balance 80  3.5* (0.01 μm*) 2.0 2.0 1.3 1.0 balance The symbol * means the value which is not within the scope of the present invention.

TABLE 40-2 Component ratio of iron-based sintered alloy (mass %) Number of Fe and inevitable piercing  Iron-based sintered alloy SrCO₃ C Mo Ni Co impurities (times) Remarks Product of the present invention 292 0.48 1.3 2 2 1 balance 278 — Comparative products 79 0.01* 1.3 2 2 1 balance 23 — 80 3.45* 1.3 2 2 1 balance 160 decrease in strength The symbol * means the value which is not within the scope of the present invention.

As is apparent from the results shown in Table 40-1 and Table 40-2, the number of piercing of the cylindrical sintered alloy block for piercing test made of the sintered alloy 292 of the present invention is larger than that of the cylindrical sintered alloy block for piercing test made of the conventional sintered alloy 46 shown in Table 18-1 to Table 18-2 and therefore the sintered alloy of the present invention is excellent in machinability. However, the comparative sintered alloy 79 containing SrCO₃ in the content of less than the range defined in the present invention is inferior in machinability because of small number of piercing, while the comparative sintered alloy 80 containing SrCO₃ in the content of more than the range defined in the present invention is excellent in machinability because of large number of piercing, but shows drastically decreased deflection strength, and therefore it is not preferred.

EXAMPLE 41

As raw powders, a SrCO₃ powder having an average particle size of 1 μm and a SUS316 (Fe-17% Cr-12% Ni-2.5% Mo) powder having an average particle size of 80 μm were prepared. These raw powders were blended according to the formulation shown in Table 41, mixed in a double corn mixer and compacted to obtain a green compact, and then the resulting green compact was sintered in a vacuum atmosphere at 0.1 Pa under the conditions of a temperature of 1200° C. and a retention time of 60 minutes to obtain an iron-based sintered alloy 293 of the present invention and comparative sintered alloys 81 to 82.

Cylindrical sintered alloy blocks for piercing test each having a diameter of 30 mm and a height of 10 mm, made of the sintered alloy 293 of the present invention and the comparative sintered alloys 81 to 82 were produced and these cylindrical sintered alloy blocks for piercing test were repeatedly pierced until the drill is damaged, using a high-speed steel drill having a diameter of 1.2 mm, under the following conditions:

-   Rotating speed: 5000 rpm -   Feed speed: 0.006 mm/rev. -   Cutting oil: none (dry).

The number of piercing (maximum number of piercing, lifetime) of one new drill was measured. The results are shown in Table 41. Machinability was evaluated by the results. TABLE 41 Component ratio Component ratio of iron-based of raw powder (mass %) sintered alloy (mass %) SUS316 (Fe—17% Fe SrCO₃ powder Cr—12% and Number of Iron-based Average particle size is Ni—2.5% Mo) inevitable piercing sintered alloy described in parenthesis. powder SrCO₃ Cr Ni Mo impurities (times) Remarks Product of the 293  0.5 (1 μm) balance 0.46 17.1 12.3 2.2 balance 182 — present invention Comparative 81 0.02* (40 μm*) balance 0.01* 17.1 12.3 2.2 balance 8 — products 82  3.5* (0.01 μm*) balance 3.45* 17.1 12.3 2.2 balance 111 decrease in strength The symbol * means the value which is not within the scope of the present invention.

As is apparent from the results shown in Table 41, the number of piercing of the cylindrical sintered alloy block for piercing test made of the sintered alloy 293 of the present invention is larger than that of the cylindrical sintered alloy block for piercing test made of the conventional sintered alloy 47 shown in 19 and therefore the sintered alloy of the present invention is excellent in machinability. However, the comparative sintered alloy 81 containing SrCO₃ in the content of less than the range defined in the present invention is inferior in machinability because of small number of piercing, while the comparative sintered alloy 82 containing SrCO₃ in the content of more than the range defined in the present invention is excellent in machinability because of large number of piercing, but shows drastically decreased deflection strength, and therefore it is not preferred.

EXAMPLE 42

As raw powders, a SrCO₃ powder having an average particle size of 1 μm and a SUS430 (Fe-17% Cr) powder having an average particle size of 80 μm were prepared. These raw powders were blended according to the formulation shown in Table 42, mixed in a double corn mixer and compacted to obtain a green compact, and then the resulting green compact was sintered in a vacuum atmosphere at 0.1 Pa under the conditions of a temperature of 1200° C. and a retention time of 60 minutes to obtain an iron-based sintered alloy 294 of the present invention and comparative sintered alloys 83 to 84.

Cylindrical sintered alloy blocks for piercing test each having a diameter of 30 mm and a height of 10 mm, made of the sintered alloy 294 of the present invention and the comparative sintered alloys 83 to 84 were produced and these cylindrical sintered alloy blocks for piercing test were repeatedly pierced until the drill is damaged, using a high-speed steel drill having a diameter of 1.2 mm, under the following conditions:

-   Rotating speed: 5000 rpm -   Feed speed: 0.006 mm/rev. -   Cutting oil: none (dry).

The number of piercing (maximum number of piercing, lifetime) of one new drill was measured. The results are shown in Table 42. Machinability was evaluated by the results. TABLE 42 Component ratio of raw powder (mass %) Component ratio of iron-based SrCO₃ powder SUS430 sintered alloy (mass %) Number of Average particle size is (Fe—17% Cr) Fe and inevitable piercing Iron-based sintered alloy described in parenthesis. powder SrCO₃ Cr impurities (times) Remarks Product of the present 294  0.5 (1 μm) balance 0.49 16.7 balance 201 — invention Comparative products 83 0.02* (40 μm*) balance 0.01* 16.7 balance 26 — 84  3.5* (0.01 μm*) balance 3.47* 16.7 balance 141 decrease in strength The symbol * means the value which is not within the scope of the present invention.

As is apparent from the results shown in Table 42, the number of piercing of the cylindrical sintered alloy block for piercing test made of the sintered alloy 294 of the present invention is larger than that of the cylindrical sintered alloy block for piercing test made of the conventional sintered alloy 48 shown in 20 and therefore the sintered alloy of the present invention is excellent in machinability. However, the comparative sintered alloy 83 containing SrCO₃ in the content of less than the range defined in the present invention is inferior in machinability because of small number of piercing, while the comparative sintered alloy 84 containing SrCO₃ in the content of more than the range defined in the present invention is excellent in machinability because of large number of piercing, but shows drastically decreased deflection strength, and therefore it is not preferred.

EXAMPLE 43

As raw powders, a SrCO₃ powder having an average particle size of 1 μm, a C powder having an average particle size of 18 μm and a SUS410 (Fe-13% Cr) powder having an average particle size of 80 μm were prepared. These raw powders were blended according to the formulation shown in Table 43, mixed in a double corn mixer and compacted to obtain a green compact, and then the resulting green compact was sintered in a vacuum atmosphere at 0.1 Pa under the conditions of a temperature of 1200° C. and a retention time of 60 minutes to obtain an iron-based sintered alloy 295 of the present invention and comparative sintered alloys 85 to 86.

Cylindrical sintered alloy blocks for piercing test each having a diameter of 30 mm and a height of 10 mm, made of the sintered alloy 295 of the present invention and the comparative sintered alloys 85 to 86 were produced and these cylindrical sintered alloy blocks for piercing test were repeatedly pierced until the drill is damaged, using a high-speed steel drill having a diameter of 1.2 mm, under the following conditions:

-   Rotating speed: 5000 rpm -   Feed speed: 0.006 mm/rev. -   Cutting oil: none (dry).

The number of piercing (maximum number of piercing, lifetime) of one new drill was measured. The results are shown in Table 43. Machinability was evaluated by the results. TABLE 43 Component ratio of iron-based Component ratio of raw powder (mass %) sintered alloy (mass %) SrCO₃ powder SUS410 Fe and Number of Iron-based Average particle size is C (Fe—13% Cr) inevitable piercing sintered alloy described in parenthesis. powder powder SrCO₃ Cr C impurities (times) Remarks Product of the 295  0.5 (1 μm) 0.15 balance 0.49 12.8 0.1 balance 147 — present invention Comparative 85 0.02* (40 μm*) 0.15 balance 0.01* 12.8 0.1 balance 7 — products 86  3.5* (0.01 μm*) 0.15 balance 3.47* 12.8 0.1 balance 106 decrease in strength The symbol * means the value which is not within the scope of the present invention.

As is apparent from the results shown in Table 43, the number of piercing of the cylindrical sintered alloy block for piercing test made of the sintered alloy 295 of the present invention is larger than that of the cylindrical sintered alloy block for piercing test made of the conventional sintered alloy 49 shown in 21 and therefore the sintered alloy of the present invention is excellent in machinability. However, the comparative sintered alloy 85 containing SrCO₃ in the content of less than the range defined in the present invention is inferior in machinability because of small number of piercing, while the comparative sintered alloy 86 containing SrCO₃ in the content of more than the range defined in the present invention is excellent in machinability because of large number of piercing, but shows drastically decreased deflection strength, and therefore it is not preferred.

EXAMPLE 44

As raw powders, a SrCO₃ powder having an average particle size of 1 m and a SUS630 (Fe-17% Cr-4% Ni-4% Cu-0.3% Nb) powder having an average particle size of 80 μm were prepared. These raw powders were blended according to the formulation shown in Table 44, mixed in a double corn mixer and compacted to obtain a green compact, and then the resulting green compact was sintered in a vacuum atmosphere at 0.1 Pa under the conditions of a temperature of 1200° C. and a retention time of 60 minutes to obtain an iron-based sintered alloy 296 of the present invention and comparative sintered alloys 87 to 88.

Cylindrical sintered alloy blocks for piercing test each having a diameter of 30 mm and a height of 10 mm, made of the sintered alloy 296 of the present invention and the comparative sintered alloys 87 to 88 were produced and these cylindrical sintered alloy blocks for piercing test were repeatedly pierced until the drill is damaged, using a high-speed steel drill having a diameter of 1.2 mm, under the following conditions:

-   Rotating speed: 5000 rpm -   Feed speed: 0.006 mm/rev. -   Cutting oil: none (dry).

The number of piercing (maximum number of piercing, lifetime) of one new drill was measured. The results are shown in Table 44. Machinability was evaluated by the results. TABLE 44 Component ratio Component ratio of raw powder of iron-based sintered alloy (mass %) (mass %) SrCO₃ powder Fe Average particle and Number of size is described #SUS630 inevitable piercing Iron-based sintered alloy in parenthesis. powder SrCO₃ Cr Ni Cu Nb impurities (times) Remarks Product of the 296  0.5 (1 μm) balance 0.45 16.8 4.1 4 0.3 balance 143 — present invention Comparative 87 0.02* (40 μm*) balance 0.01* 16.8 4.1 4 0.3 balance 13 — products 88  3.5* (0.01 μm*) balance 3.43* 16.8 4.1 4 0.3 balance 108 decrease in strength #SUS630 (Fe—17% Cr—4% Ni—4% Cu-0.3% Nb) The symbol * means the value which is not within the scope of the present invention.

As is apparent from the results shown in Table 44, the number of piercing of the cylindrical sintered alloy block for piercing test made of the sintered alloy 296 of the present invention is larger than that of the cylindrical sintered alloy block for piercing test made of the conventional sintered alloy 50 shown in 22 and therefore the sintered alloy of the present invention is excellent in machinability. However, the comparative sintered alloy 87 containing SrCO₃ in the content of less than the range defined in the present invention is inferior in machinability because of small number of piercing, while the comparative sintered alloy 88 containing SrCO₃ in the content of more than the range defined in the present invention is excellent in machinability because of large number of piercing, but shows drastically decreased deflection strength, and therefore it is not preferred.

INDUSTRIAL APPLICABILITY

The iron-based sintered alloy containing a machinability improving component comprising CaCO₃ and the iron-based sintered alloy containing a machinability improving component comprising SrCO₃ according to the present invention are excellent in machinability. Therefore, in various electric and machine components made of the iron-based sintered alloys of the present invention, the cost of machining such as piercing, cutting or grinding can be reduced. Thus, the present invention can contribute largely toward the development of mechanical industry by providing various machine components, which require dimensional accuracy, at low cost. 

1. An iron-based sintered alloy having excellent machinability, comprising 0.05 to 3% by mass of calcium carbonate.
 2. An iron-based sintered alloy having excellent machinability with the composition consisting of 0.05 to 3% by mass of calcium carbonate, the balance being Fe and inevitable impurities.
 3. An iron-based sintered alloy having excellent machinability with the composition consisting of 0.05 to 3% by mass of calcium carbonate and 0.1 to 1.5% by mass of P, the balance being Fe and inevitable impurities.
 4. An iron-based sintered alloy having excellent machinability with the composition consisting of 0.05 to 3% by mass of calcium carbonate and 0.1 to 1.2% by mass of C, the balance being Fe and inevitable impurities.
 5. An iron-based sintered alloy having excellent machinability with the composition consisting of 0.05 to 3% by mass of calcium carbonate, 0.1 to 1.2% by mass of C and 10 to 25% by mass of Cu, the balance being Fe and inevitable impurities.
 6. An iron-based sintered alloy having excellent machinability with the composition consisting of 0.05 to 3% by mass of calcium carbonate, 0.1 to 1.2% by mass of C and 0.1 to 6% by mass of Cu, the balance being Fe and inevitable impurities.
 7. An iron-based sintered alloy having excellent machinability with the composition consisting of 0.05 to 3% by mass of calcium carbonate, 0.1 to 1.2% by mass of C, 0.1 to 6% by mass of Cu, 0.1 to 10% by mass of Ni and 0.1 to 6% by mass of Mo, the balance being Fe and inevitable impurities.
 8. An iron-based sintered alloy having excellent machinability with the composition consisting of 0.05 to 3% by mass of calcium carbonate, 0.1 to 1.2% by mass of C and 0.1 to 6% by mass of Mo, the balance being Fe and inevitable impurities.
 9. An iron-based sintered alloy having excellent machinability with the composition consisting of 0.05 to 3% by mass of calcium carbonate, 0.1 to 1.2% by mass of C, 0.1 to 10% by mass of Cr and 0.1 to 6% by mass of Mo, the balance being Fe and inevitable impurities.
 10. An iron-based sintered alloy having excellent machinability with the composition consisting of 0.05 to 3% by mass of calcium carbonate, 0.1 to 1.2% by mass of C, 0.1 to 10% by mass of Ni, 0.1 to 10% by mass of Cr and 0.1 to 6% by mass of Mo, the balance being Fe and inevitable impurities.
 11. An iron-based sintered alloy having excellent machinability with the composition consisting of 0.05 to 3% by mass of calcium carbonate, 0.1 to 1.2% by mass of C, 0.1 to 6% by mass of Cu, 0.1 to 10% by mass of Ni, 0.1 to 10% by mass of Cr and 0.1 to 6% by mass of Mo, the balance being Fe and inevitable impurities.
 12. An iron-based sintered alloy having excellent machinability with the composition consisting of 0.05 to 3% by mass of calcium carbonate, 0.1 to 1.2% by mass of C and 0.1 to 10% by mass of Ni, the balance being Fe and inevitable impurities.
 13. An iron-based sintered alloy having excellent machinability with the composition consisting of 0.05 to 3% by mass of calcium carbonate, 0.1 to 1.2% by mass of C, 0.1 to 10% by mass of Ni and 0.1 to 6% by mass of Mo, the balance being Fe and inevitable impurities.
 14. An iron-based sintered alloy having excellent machinability with the composition consisting of 0.05 to 3% by mass of calcium carbonate, 0.1 to 1.2% by mass of C, 0.1 to 6% by mass of Cu and 0.1 to 10% by mass of Ni, the balance being Fe and inevitable impurities.
 15. An iron-based sintered alloy having excellent machinability with the composition consisting of 0.05 to 3% by mass of calcium carbonate, 1.0 to 3.0% by mass of C, 0.5 to 8% by mass of Cu and 0.1 to 0.8% by mass of P, the balance being Fe and inevitable impurities.
 16. An iron-based sintered alloy having excellent machinability with the composition consisting of 0.05 to 3% by mass of calcium carbonate, 0.3 to 2.5% by mass of C, 0.5 to 12% by mass of Cr, 0.3 to 9% by mass of Mo, 3 to 14% by mass of W and 1 to 6% by mass of V, the balance being Fe and inevitable impurities.
 17. An iron-based sintered alloy having excellent machinability with the composition consisting of 0.05 to 3% by mass of calcium carbonate, 0.3 to 2.5% by mass of C, 0.5 to 12% by mass of Cr, 0.3 to 9% by mass of Mo, 3 to 14% by mass of W, 1 to 6% by mass of V and 5 to 14% by mass of Co, the balance being Fe and inevitable impurities.
 18. An iron-based sintered alloy having excellent machinability with the composition consisting of 0.05 to 3% by mass of calcium carbonate, 0.3 to 2% by mass of C, 0.5 to 10% by mass of Cr, 0.3 to 16% by mass of Mo and 0.1 to 5% by mass of Ni, and one or more kinds selected from among 1 to 5% by mass of W, 0.05 to 1% by mass of Si, 0.5 to 18% by mass of Co and 0.05 to 2% by mass of Nb, the balance being Fe and inevitable impurities.
 19. An iron-based sintered alloy having excellent machinability with the composition consisting of 0.05 to 3% by mass of calcium carbonate, 0.3 to 2% by mass of C, 0.5 to 10% by mass of Cr, 0.3 to 16% by mass of Mo and 0.1 to 5% by mass of Ni, one or more kinds selected from among 1 to 5% by mass of W, 0.05 to 1% by mass of Si, 0.5 to 18% by mass of Co and 0.05 to 2% by mass of Nb, and 10 to 20% by mass of Cu, the balance being Fe and inevitable impurities.
 20. An iron-based sintered alloy having excellent machinability with the composition consisting of 0.05 to 3% by mass of calcium carbonate, 0.3 to 2% by mass of C, 0.1 to 3% by mass of Mo, 0.05 to 5% by mass of Ni and 0.1 to 2% by mass of Co, the balance being Fe and inevitable impurities.
 21. An iron-based sintered alloy having excellent machinability with the composition consisting of 0.05 to 3% by mass of calcium carbonate, 15 to 27% by mass of Cr and 3 to 29% by mass of Ni, the balance being Fe and inevitable impurities.
 22. An iron-based sintered alloy having excellent machinability with the composition consisting of one or more kinds selected from among 0.05 to 3% by mass of calcium carbonate, 15 to 27% by mass of Cr, 3 to 29% by mass of Ni, 0.5 to 7% by mass of Mo and 0.5 to 4% by mass of Cu, the balance being Fe and inevitable impurities.
 23. An iron-based sintered alloy having excellent machinability with the composition consisting of 0.05 to 3% by mass of calcium carbonate and 10 to 33% by mass of Cr, the balance being Fe and inevitable impurities.
 24. An iron-based sintered alloy having excellent machinability with the composition consisting of 0.05 to 3% by mass of calcium carbonate, 10 to 33% by mass of Cr and 0.5 to 3% by mass of Mo, the balance being Fe and inevitable impurities.
 25. An iron-based sintered alloy having excellent machinability with the composition consisting of 0.05 to 3% by mass of calcium carbonate, 10 to 19% by mass of Cr and 0.05 to 1.3% by mass of C, the balance being Fe and inevitable impurities.
 26. An iron-based sintered alloy having excellent machinability with the composition consisting of 0.05 to 3% by mass of calcium carbonate, 14 to 19% by mass of Cr and 2 to 8% by mass of Ni, the balance being Fe and inevitable impurities.
 27. An iron-based sintered alloy having excellent machinability with the composition consisting of 0.05 to 3% by mass of calcium carbonate, 14 to 19% by mass of Cr and 2 to 8% by mass of Ni, and one or more kinds selected from among 2 to 6% by mass of Cu, 0.1 to 0.5% by mass of Nb and 0.5 to 1.5% by mass of Al, the balance being Fe and inevitable impurities.
 28. The iron-based sintered alloy having excellent machinability according to claim 1, wherein the calcium carbonate is dispersed at grain boundary in a basis material of the iron-based sintered alloy.
 29. A method for preparing the iron-based sintered alloy having excellent machinability according to claim 1, which comprises compacting a raw powder mixture containing 0.05 to 3% by mass of a calcium carbonate powder having an average particle size of 0.1 to 30 μm as a raw powder to obtain a green compact and sintering the resulting green compact in a nonoxidizing gas atmosphere.
 30. An iron-based sintered alloy having excellent machinability, comprising 0.05 to 3% by mass of strontium carbonate.
 31. An iron-based sintered alloy having excellent machinability with the composition consisting of 0.05 to 3% by mass of strontium carbonate, the balance being Fe and inevitable impurities.
 32. An iron-based sintered alloy having excellent machinability with the composition consisting of 0.05 to 3% by mass of strontium carbonate and 0.1 to 1.5% by mass of P, the balance being Fe and inevitable impurities.
 33. An iron-based sintered alloy having excellent machinability with the composition consisting of 0.05 to 3% by mass of strontium carbonate and 0.1 to 1.2% by mass of C, the balance being Fe and inevitable impurities.
 34. An iron-based sintered alloy having excellent machinability with the composition consisting of 0.05 to 3% by mass of strontium carbonate, 0.1 to 1.2% by mass of C and 10 to 25% by mass of Cu, the balance being Fe and inevitable impurities.
 35. An iron-based sintered alloy having excellent machinability with the composition consisting of 0.05 to 3% by mass of strontium carbonate, 0.1 to 1.2% by mass of C and 0.1 to 6% by mass of Cu, the balance being Fe and inevitable impurities.
 36. An iron-based sintered alloy having excellent machinability with the composition consisting of 0.05 to 3% by mass of strontium carbonate, 0.1 to 1.2% by mass of C, 0.1 to 6% by mass of Cu, 0.1 to 10% by mass of Ni and 0.1 to 6% by mass of Mo, the balance being Fe and inevitable impurities.
 37. An iron-based sintered alloy having excellent machinability with the composition consisting of 0.05 to 3% by mass of strontium carbonate, 0.1 to 1.2% by mass of C and 0.1 to 6% by mass of Mo, the balance being Fe and inevitable impurities.
 38. An iron-based sintered alloy having excellent machinability with the composition consisting of 0.05 to 3% by mass of strontium carbonate, 0.1 to 1.2% by mass of C, 0.1 to 10% by mass of Cr and 0.1 to 6% by mass of Mo, the balance being Fe and inevitable impurities.
 39. An iron-based sintered alloy having excellent machinability with the composition consisting of 0.05 to 3% by mass of strontium carbonate, 0.1 to 1.2% by mass of C, 0.1 to 10% by mass of Ni, 0.1 to 10% by mass of Cr and 0.1 to 6% by mass of Mo, the balance being Fe and inevitable impurities.
 40. An iron-based sintered alloy having excellent machinability with the composition consisting of 0.05 to 3% by mass of strontium carbonate, 0.1 to 1.2% by mass of C, 0.1 to 6% by mass of Cu, 0.1 to 10% by mass of Ni, 0.1 to 10% by mass of Cr and 0.1 to 6% by mass of Mo, the balance being Fe and inevitable impurities.
 41. An iron-based sintered alloy having excellent machinability with the composition consisting of 0.05 to 3% by mass of strontium carbonate, 0.1 to 1.2% by mass of C and 0.1 to 10% by mass of Ni, the balance being Fe and inevitable impurities.
 42. An iron-based sintered alloy having excellent machinability with the composition consisting of 0.05 to 3% by mass of strontium carbonate, 0.1 to 1.2% by mass of C, 0.1 to 10% by mass of Ni and 0.1 to 6% by mass of Mo, the balance being Fe and inevitable impurities.
 43. An iron-based sintered alloy having excellent machinability with the composition consisting of 0.05 to 3% by mass of strontium carbonate, 0.1 to 1.2% by mass of C, 0.1 to 6% by mass of Cu and 0.1 to 10% by mass of Ni, the balance being Fe and inevitable impurities.
 44. An iron-based sintered alloy having excellent machinability with the composition consisting of 0.05 to 3% by mass of strontium carbonate, 1.0 to 3.0% by mass of C, 0.5 to 8% by mass of Cu and 0.1 to 0.8% by mass of P, the balance being Fe and inevitable impurities.
 45. An iron-based sintered alloy having excellent machinability with the composition consisting of 0.05 to 3% by mass of strontium carbonate, 0.3 to 2.5% by mass of C, 0.5 to 12% by mass of Cr, 0.3 to 9% by mass of Mo, 3 to 14% by mass of W and 1 to 6% by mass of V, the balance being Fe and inevitable impurities.
 46. An iron-based sintered alloy having excellent machinability with the composition consisting of 0.05 to 3% by mass of strontium carbonate, 0.3 to 2.5% by mass of C, 0.5 to 12% by mass of Cr, 0.3 to 9% by mass of Mo, 3 to 14% by mass of W, 1 to 6% by mass of V and 5 to 14% by mass of Co, the balance being Fe and inevitable impurities.
 47. An iron-based sintered alloy having excellent machinability with the composition consisting of 0.05 to 3% by mass of strontium carbonate, 0.3 to 2% by mass of C, 0.5 to 10% by mass of Cr, 0.3 to 16% by mass of Mo and 0.1 to 5% by mass of Ni, and one or more kinds selected from among 1 to 5% by mass of W, 0.05 to 1% by mass of Si, 0.5 to 18% by mass of Co and 0.05 to 2% by mass of Nb, the balance being Fe and inevitable impurities.
 48. An iron-based sintered alloy having excellent machinability with the composition consisting of 0.05 to 3% by mass of strontium carbonate, 0.3 to 2% by mass of C, 0.5 to 10% by mass of Cr, 0.3 to 16% by mass of Mo and 0.1 to 5% by mass of Ni, one or more kinds selected from among 1 to 5% by mass of W, 0.05 to 1% by mass of Si, 0.5 to 18% by mass of Co and 0.05 to 2% by mass of Nb, and 10 to 20% by mass of Cu, the balance being Fe and inevitable impurities.
 49. An iron-based sintered alloy having excellent machinability with the composition consisting of 0.05 to 3% by mass of strontium carbonate, 0.3 to 2% by mass of C, 0.1 to 3% by mass of Mo, 0.05 to 5% by mass of Ni and 0.1 to 2% by mass of Co, the balance being Fe and inevitable impurities.
 50. An iron-based sintered alloy having excellent machinability with the composition consisting of 0.05 to 3% by mass of strontium carbonate, 15 to 27% by mass of Cr and 3 to 29% by mass of Ni, the balance being Fe and inevitable impurities.
 51. An iron-based sintered alloy having excellent machinability with the composition consisting of one or more kinds selected from among 0.05 to 3% by mass of strontium carbonate, 15 to 27% by mass of Cr, 3 to 29% by mass of Ni, 0.5 to 7% by mass of Mo and 0.5 to 4% by mass of Cu, the balance being Fe and inevitable impurities.
 52. An iron-based sintered alloy having excellent machinability with the composition consisting of 0.05 to 3% by mass of strontium carbonate and 10 to 33% by mass of Cr, the balance being Fe and inevitable impurities.
 53. An iron-based sintered alloy having excellent machinability with the composition consisting of 0.05 to 3% by mass of strontium carbonate, 10 to 33% by mass of Cr and 0.5 to 3% by mass of Mo, the balance being Fe and inevitable impurities.
 54. An iron-based sintered alloy having excellent machinability with the composition consisting of 0.05 to 3% by mass of strontium carbonate, 10 to 19% by mass of Cr and 0.05 to 1.3% by mass of C, the balance being Fe and inevitable impurities.
 55. An iron-based sintered alloy having excellent machinability with the composition consisting of 0.05 to 3% by mass of strontium carbonate, 14 to 19% by mass of Cr and 2 to 8% by mass of Ni, the balance being Fe and inevitable impurities.
 56. An iron-based sintered alloy having excellent machinability with the composition consisting of 0.05 to 3% by mass of strontium carbonate, 14 to 19% by mass of Cr and 2 to 8% by mass of Ni, and one or more kinds selected from among 2 to 6% by mass of Cu, 0.1 to 0.5% by mass of Nb and 0.5 to 1.5% by mass of Al, the balance being Fe and inevitable impurities.
 57. The iron-based sintered alloy having excellent machinability according to claim 30, wherein the strontium carbonate is dispersed at grain boundary in a basis material of the iron-based sintered alloy.
 58. A method for preparing the iron-based sintered alloy having excellent machinability according to claim 30, which comprises compacting a raw powder mixture containing 0.05 to 3% by mass of a strontium carbonate powder having an average particle size of 0.1 to 30 μm as a raw powder to obtain a green compact and sintering the resulting green compact in a nonoxidizing gas atmosphere. 